Course 4 Flashcards

Question

Tetrahydrofolate (derivative B9)

Answer 1

- under normal circumstances, tetrahydrofolate is the donor of mono-carbon residues - methyl / formyl / methylene-tetrahydrofolate transfers a single-carbon residue, tetrahydrofolate is formed and it is "charged" again, eg by the reaction serine -> glycine O the exception is thymidine synthesis , wherein upon transfer of the carbonaceous residue, the tetrahydrofolate is oxidized to dihydrofolate, which is completely useless and must first be reduced back to tetrahydrofolate in order to be recovered and useful O if the enzyme dihydrofolate reductase that reduces dihydrofolate is blocked, all reactions that use tetrahydrofolate as a cofactor will be blocked as well - the tetrahydrofolate forms are freely convertible with one another, except for methyl tetrahydrofolate O methyl tetrahydrofolate cannot be converted into anything else and the only way to get that monocarbon residue is to get rid of (and thus convert to tetrahydrofolate) is the synthesis of methionine from homocysteine O synthesis of methionine from homocysteine has one cofactor - vitamin B12 O it follows that in the absence of B12, methyl tetrahydrofolate will accumulate, so the body will not have enough tetrahydrofolate for nucleic acid synthesis § = we need vitamin B12 to recycle vitamin B9 § = in case of B12 deficiency, the body will also show signs of B9 deficiency = important !!

Answer 2

- binding of PRPP , more common in purines - adenine binds to PRPP to form AMP; APRT enzyme (adenine phosphoribosil transferase) - guanine binds to PRPP, GMP is formed; HGPRT enzyme (hypoxanthine-guanine phosphoribosil transferase) - the HGPRT defect is called Lesch-Nyhan syndrome O symptoms - hyperuricemia, behavioral disorders (extreme psychotic self-harm, mental retardation),high concentration of PRPP, which stimulates further synthesis of products (thanks to positive feedback) = overproduction of waste products

Answer 3

- complete decomposition except for water and ammonia - 2 intermediates: β-alanine (in uracil and cytosine) and β-amino isobutyrate (for thymine)

Answer 4

- all purines decompose to the final product which is uric acid (trihydroxypurine) - uric acid is poorly soluble in water => even a small increase leads to crystallization and gout disease - the enzyme that forms uric acid is Xanthine oxidase ( hypoxanthine -> xanthine -> uric acid) O Xanthine oxidase contains an element Molybdenum

Answer 5

- one identical helix is created from one double helix - semiconservative character - each of the daughter helices has one original (template) and one new (complementary) helix - the synthesis proceeds from the 5 'to the 3' end ( 5 'is the 5th carbon on deoxyribose bearing a phosphorus moiety and 3' is the 3rd carbon on deoxyribose bearing an OH group; The 5 'end is thus the end of the helix where the phosphorus group is free, the 3' end is where the OH is free) O the newly formed fiber is therefore oriented 5 '-> 3' O and because the helices join each other in opposite directions, the template must be 3 '-> 5'

Answer 6

Replicon (a segment of DNA): replication unit with its own replication origin. Procaryotic chromosome: one replicon Eucaryotic chromosome: many (hundreds and thousands) replicons Replication origin: a specific sequence of DNA (rich in A-T pairs) where the replications starts. Replication fork: the replication continues from the replication origin in both opposite directions → two replication forks moving apart (the shape of letter Y). Procaryotic chromosome: replication fork moves at 1000bp/s. Eucaryotic chromosome: replication fork moves at 100bp/s.

Answer 7

it catalyzes the formation of phosphodiester bond between two nucleotides (3´end and 5´end of deoxyriboses) via relevant phosphate. The newly added nucleotide of growing DNA strand: first, complementary pairing with the base of relevant nucleotide of the template, afterwards, the formation of phosphodiester bond with the previous nucleotide of growing strand Nucleotide enters the reaction as nucleoside triphosphate. Energy released by freeing pyrophosphate (PPi) is used for polymerization reaction. Two important and limiting properties of DNA polymerase: * It can synthesize new DNA strand only in 5´→3´ direction (according to the template in 3´→5´ direction)! * It is unable to start the synthesis of new DNA strand, it can only extend the existing strand of nucleic acid. DNA polymerases of eukaryotic cell: * DNA polymerase α * DNA polymerase δ and other types (DNA polymerase β)

Answer 8

* Helicase: after the binding to replication origin, it unwinds the double helix of DNA (energy from ATP is used). * Single-strand binding protein: molecules of the protein stabilize single-stranded DNA by binding to it. * Primase: it starts the replication by the formation of a short RNA strand (primer). Primer provides DNA polymerase with 3´ end, DNA polymerase continues the synthesis of new DNA strand according to the template. primer in procaryotic cell: 5 bp primer in eucaryotic cell: 10 bp * Protein sliding clamp: it keeps DNA polymerase attached to the template strand and it allows DNA polymerase to slide along the strand.

Answer 9

leading strand Synthesis of new strand in 5´→3´on template 3´→5´ synthesis runs continuously (DNA polymerase δ) Lagging strand Synthesis of new strand in 3´ →5´ direction on 5´→3´ template: Synthesis runs discontinously (DNA polymerase α) Lagging strand: DNA polymerase „skips“ here forward along the template and then it synthesizes backwards in proper direction 5´→3´. The synthesis of new strand is performed piece after piece and these pieces are referred to as Okazaki fragments (each fragment starts with its own primer). Afterwards, RNA primers are removed, missing DNA is synthesized by relevant DNA polymerase and finally individual fragments are joined by DNA ligase. Okazaki fragments of procaryotic cell: about 1000 nucleotides Okazaki fragments of eucaryotic cell: about 200 nucleotides

Answer 10

A problem of synthesizing the lagging strand at the end of chromosomes (telomere): it is solved by telomerase Telomerase: adds short repeats of a DNA sequence to the 3´end it uses a RNA template that is part of the enzyme Repetitive DNA sequence then acts as a template to complete replication of the end of lagging strand.

Answer 11

It is a correcting activity of DNA polymerase on new DNA strand in 3´→5´ direction while it synthesizes new strand in 5´→3´ direction. Functioning of DNA polymerase before binding a new nucleotide: * It verifies whether previously bound nucleotide has the base complementary to the template * If yes, it continues by binding a new nucleotide * If no, it removes the previous wrong nucleotide and, instead of this nucleotide, the corresponding nucleotide is bound Proofreading activity of DNA polymerase explains why DNA polymerase has only 5´→3´ polymerase activity and proofreading in 3´→5´ direction. Proofreading in 5´→3´ direction (hypothetical polymerization in 3´→5´ direction) is not possible from the chemical point of view.

Answer 12

Mismatch repair: it corrects wrongly paired bases of newly synthesized DNA strand (it corrects mistakes of replication machinery). Proteins, involved in mismatch repair, recognize pairing which is not complementary (mismatch) due to the deformation of DNA double helix. Afterwards, they remove wrong segment of new DNA strand and synthesize this segment again. Replication machinery: 1 error/107 nucleotides Mismatch repair: correction of 99% errors of replication machinery →Overall accuracy of DNA replication: 1 error/109 nucleotides

Answer 13

* Depurination: release of guanine or adenine from DNA (spontaneous) * Deamination: conversion of cytosine to uracil (spontaneous) * Formation of pyrimidine (thymine) dimers: caused by UV irradiation

Answer 14

General steps of the repair of damaged DNA: * recognition of the damage of DNA strand → Excision of the damaged DNA by specific nucleases * synthesis of removed DNA according to complementary strand by repair DNA polymerases * rejoining newly synthesized DNA segment with repaired DNA strand by DNA ligase (ligation) * Base excision repair * Nucleotide excision repair The stability of DNA and thus also the stability of genetic information depends on mechanisms of DNA repair.

Answer 15

Transcription: synthesis of new complementary RNA strand according to DNA template (copying genetic information from DNA). Synthesis of new RNA strand is catalyzed by RNA polymerase. During transcription, one strand of DNA double helix serves as a template (template strand) while the second strand is referred to as coding strand.

Answer 16

RNA polymerase: it catalyzes the formation of phosphodiester bond between subsequent ribonucleotides. Properties of RNA polymerase: * It has only 5´→3´ polymerase activity (similarly like DNA polymerase) according to template in 3´→5´ direction * It is able to start the synthesis of new RNA strand (on the contrary to DNA polymerase) 3 types of RNA polymerase in eucaryotic cell: * RNA polymerase I: genes for most of rRNAs (with the exception of 5S rRNA) * RNA polymerase II: all genes encoding proteins, genes of some small RNAs * RNA polymerase III: genes encoding tRNAs, gene for 5S rRNA, genes of some small RNAs

Answer 17

Initiation of transcription: RNA polymerase binds to the promoter of gene which will be translated. Promotor: a sequence of DNA that indicates the point where the transcription starts. Promoter is located before the first transcribed nucleotide. It contains TATA box (formed mainly by T and A nucleotides). RNA polymerase binding to promoter: General transcription factors are involved in the binding. Promotor is asymmetrical and it always binds RNA polymerase in one direction while RNA polymerase can transcribe DNA templates only in a 3´→5´ direction. →Proper strand is only transcribed, i.e. template strand.

Answer 18

RNA polymerase unwinds in front of it a short segment of DNA double helix (accessibility of template DNA strand for transcription) → RNA polymerase adds to the first transcribed DNA nucleotide complementary RNA nucleotide and thus the transcription is started. Elongation phase of transcription: RNA polymerase continues along the template DNA strand, it unwinds ahead a short segment of DNA double helix and at the same time it synthesizes new RNA strand on the basis of complementary pairing with the bases of template strand. During transcription, a short hybrid double-stranded segment of DNA RNA is formed transiently. However, newly synthesized RNA strand is released from binding to DNA soon.

Answer 19

In bacteria, signal for the termination is a specific DNA sequence (terminator). In eucaryotes, the mechanism of termination differs for individual RNA polymerases (so far it is not fully clarified) → The release of RNA polymerase from binding to DNA and at the same time the release of newly transcribed RNA strand. Transcription machinery: 1 error/104 nucleotides

Answer 20

Posttranscriptional RNA processing: modifications of RNA after its transcription in the nucleus of the eucaryotic cell and before its transport into cytoplasm and its translation. Modifications of both ends of transcribed RNA strand: * RNA capping: 7-methylguanosine is bound to the 5´end by the unusual 5´→5´ linkage via a bridge made of 3 phosphates (cap). * RNA polyadenylation: repeated adenine nucleotides (100-200) are bound to the 3´end (poly-A end). These two modifications increase the stability of mRNA

Answer 21

noncoding sequenses (introns) are removed from primary transcript and coding sequenses (exons) are joined in given order. Completed mRNA, which is ready for translation, is formed by the posttranscriptional processing.

Answer 22

Introns are often longer than exons. Exons (in an average gene): ~ 1000 nucleotides Introns (in an average gene): 5000-20 000 nucleotides Spliceosomes: large complexes of ribonucleoproteins and proteins which carry out splicing. Present ribonucleoproteins contain small nuclear RNAs (snRNAs). Small nuclear RNAs recognize exon-intron boundaries and they form small nuclear ribonucleoprotein particles (snRNPs) referred to as „snurps“. „Snurps“ form the core of spliceosome.

Answer 23

at the place of relevant intron, a loop is formed due to the interaction of spliceosome with RNA → ends of neighboring exons get closer → RNA strand between intron and exon is interrupted and corresponding ends of neighboring exons are joined → the loop of excised intron is released and at the same time components of spliceosome are released Evolutionary significance of intron existence: * Possibility of alternative splicing (more proteins from one gene). * Increased probability of genetic recombination between exons of different genes.

Answer 24

Translation: the synthesis of new polypeptide chain (protein) according to genetic information saved in corresponding mRNA. The sequence of amino acids is determined by the sequence of bases in corresponding mRNA. It happens on the basis of genetic code. It is a turn (translation) from the language of nucleotides into the language of amino acids. Translation apparatus reads mRNA in 5´→3´ direction. New polypeptide chain is synthesized from the N end towards the C end

Answer 25

Translation is carried out on ribosomes. Together with mRNA (it is carrying genetic information), tRNA plays a key role during translation. Individual types of tRNA function as adaptors recognizing corresponding codon for amino acid which they carry

Answer 26

Ribosome: a large complex that comprises several types of rRNA and a big number of various proteins. Eucaryotic ribosome (80S ribosome): * Small subunit: 1 type of rRNA (18S) & 33 proteins. * Large subunit: 3 types of rRNA (5S, 5.8S, 28S) & 49 proteins. There are 4 specific binding sites on ribosome: * mRNA binding site and three tRNA binding sites, i.e. * A site (aminoacyl-tRNA): it binds tRNA carrying relevant amino acid * P site (peptidyl-tRNA): it binds peptidyl-tRNA (peptide bound to tRNA) * E site (exit): tRNA is released from ribosome here

Answer 27

tRNA: about 80 nucleotides, it contains some minor bases and nucleotides derived from them (pseudouridine - ψ, dihydrouridine - D). Structure of tRNA: 4 short double-stranded segments (complementary pairing) 3 double-stranded segments are terminated by single-stranded loop it has a character of clover leaf Relevant amino acid is bound at the 3´end (terminal sequence of CCA) by energy-rich bond. Energy of this bond is used for the formation of peptide bond during translation.

Answer 28

sequence of 3 nucleotides of tRNA which is complementary to the triplet of bases on mRNA encoding amino acid carried by this tRNA. Some of tRNAs require, for binding to mRNA during translation, precise complementary pairing only on the first two positions of codon. → For amino acid encoded by more triplets with the same first two bases, only one tRNA is sufficient for translation. Thus only 31 types of tRNA are sufficient for 20 amino acids encoded by 61 codons.

Answer 29

performs binding of amino acid to relevant tRNA with corresponding anticodon. Each amino acid has own specific aminoacyl-tRNA synthetase. These synthetases carry out decoding of the genetic code

Answer 30

The translation of mRNA always starts with the codon AUG which encodes methionine. → Every new polypeptide chain starts with methionine. A specific initiator tRNA carrying methionine is required for the initiation of translation. Initiation of translation: Binding of the initiator tRNA together with other initiator factors to the small ribosomal subunit → complex binds to the 5´end of mRNA (it recognizes the cap) → it slides along mRNA in 5´→3´ direction until it recognizes the first AUG codon → the large subunit binds (ribosome is completed) while the initiator tRNA is bound at the P site → further aminoacyl-tRNA, with the anticodon corresponding to the second codon of mRNA after AUG, binds at the A site

Answer 31

It starts by binding of further aminoacyl-tRNA at the A site → polypeptide chain is released from tRNA at the P site and it is bound by peptide bond to the amino acid carried by the tRNA at the A site → at the same time tRNA carrying prolonged polypeptide chain is shifted from the A site to the P site and now free tRNA is shifted from the P site to E site → thus, the A site is free for binding of further aminoacyl-tRNA → in the last step, tRNA is released from the E site and whole the cycle of elongation can be repeated Peptidyl transferase: it catalyzes the formation of peptide bond, it is a part of the large ribosomal subunit.

Answer 32

It takes place when one of the three stop codons (UAA, UAG, UGA) appears at the A site → stop codons are not recognized by any tRNA and protein release factors are bound instead of tRNA → a consequence is that peptidyl transferase catalyzes the binding of water molecule instead of amino acid → polypeptide chain is terminated and it is released from the ribosome Polyribosomes: the initiation of translation happens repeatedly on individual mRNA molecules → several ribosomes perform translation on one mRNA molecule at the same time

Answer 33

- DNA diagnostics deals with gene sequences and repetitive sequences of non-coding regions - RNA diagnostics and protein diagnostics deal with gene expression - nucleic acid sources O DNA - all nuclear cells (ideally blood) O RNA - only cells where the gene is expressed (because there is a different RNA in each tissue due to cell differentiation)

Answer 34

-are able to detect: O monogenic and polygenic hereditary diseases O some types of tumors (protooncogenes and tumor suppressor genes) O infection present (pathogens being sought) O disease progression during treatment O identification of people in forensic medicine (individual people differ from each other mainly by repetitive sequences) O HLA-typing (HLA is a complex of genes responsible for the detection of foreign particles) - during transplantation

Answer 35

- preimplantation - embryo testing before artificial insemination - prenatal - prenatal screening in high-risk pregnancies (not without risk for the child, parental consent required) - presymptomatic - neonatal screening

Answer 36

- DNA sequence variability between different individuals of the same species - DNA polymorphism - physiological; the occurrence of the allele in at least 1% of the population determines the predisposition to polygenic diseases - mutation - pathological; the occurrence of the allele is not even in 1% of the population, it causes monogenic diseases

Answer 37

- a polymorphism of a given predisposing gene is detected - targeted analysis - we know the sequence and localization of the gene, we know the nature of the mutation (deletion / substitution / ...) O We are going to be sure to look at a specific point in DNA O DNA is isolated -> PCR (multiplication of isolated DNA) + further analysis -> visualization (electrophoresis) O examination of the family is not necessary - complete analysis - we know the sequence and localization of the gene, but we do not know exactly which mutation it is O necessary examination of other family members (because we are trying to find out exactly what nucleotides are located in this sequence of genes of a healthy and a sick family member, compare them and find a mutated nucleotide)

Answer 38

- basic steps O lysis of the cells and release of the DNA into solution O removal of proteins by cleavage, adsorption or extraction § we do not want proteins in solution because they would inhibit the following steps O precipitation of DNA - DNA precipitates and can be washed -> removal of impurities O dissolving DNA in water or buffer

Answer 39

- protein concentration is measured - spectrophotometry - adsorption maximum for DNA is 260nm, for proteins 280nm O with the ratio 260/280 we find the purity of DNA (the higher the ratio the cleaner the DNA) - gel electrophoresis with fluorescent dyes O The DNA with the bound colors is visible in the gel O the gel contains a DNA sample of known concentration - then only the light intensities are compared (highly indicative)

Answer 40

- size distribution of DNA fragments (RNA, proteins) on the principle of moving charged particles in an electric field - DNA contains negatively charged phosphate groups -> movement from cathode (-) to anode (+) - the speed of movement is inversely proportional to the length of the fragment - gel - network structure of polymer molecules with pores O polyacrylamide - able to distinguish DNA fragments differing by one nucleotide O agarose - divides nucleotides differing by at least 10 nucleotides, preferably used on DNA - ethidium bromide - the color added to the gel binds to DNA and glows under UV

Answer 41

- principle: multiplication (amplification) of a selected section of DNA - the only PCR control constant is the temperature - basic components of PCR O DNA sample O two types of primers O free nucleotides (dATP, dTTp, dCTP, dGTP) O DNA polymerase with buffer

Answer 42

- short DNA oligonucleotides (20-30 nucleotides) binding to a specific site on the DNA - each primer binds to one strand of a double helix, one primer is called forward and the other reverse - serves as a replication start - delimit the target region of the DNA we want to amplify (template strand for replication must be 3 '-> 5' and the primer indicates the start of replication, so the primers bind to the 3 'edge of the target DNA) - annealing of the trimmers is affected by temperature - it is necessary to create hydrogen bonds, the length of the primers and the content of nucleotides raise the required temperature (CG needs a higher temperature than AT)

Answer 43

- PCR takes place in cycles (30-40) and each cycle has 3 steps 1) denaturation - reversible separation of individual DNA strands by breaking the hydrogen bonds between complementary nucleotides at a temperature of at least 94 ° C 2) annealing - attaching primers to separate strands of DNA O the minimum temperature depends on the primer used 3) extension (elongation) - elongation, synthesis of a new DNA strand using DNA polymerase O we need 72 ° C, but human DNA polymerase would not withstand it, so living bacteria DNA polymerase is used in hot springs, so-called TAQ polymerase

Answer 44

- PCR with allele-specific primers (ASO-PCR) O when we know exactly what mutation there is -> the primer will only fit on it O targeted analysis - 2 separate tubes are used § 2 primers are used - one of the pair binds directly to the site of the possible mutation and one somewhere to the surroundings § in the 1st tube the allele-specific primer is complementary to the healthy allele, it only mounts if the mutation did not happen § in the 2nd tube the allele-specific primer is complementary to the mutation, it only mounts if the mutation has occurred § if a reaction occurs in both tubes -> heterozygous - PCR with general primers O amplification always occurs, then targeted, complete analysis O we use it if we don't know what it is - we need more general primers O we will use general primers in targeted and complete analysis

Answer 45

- nested PCR - 2x PCR with general primers, another PCR reaction is performed on the result of one PCR O used for old or bacterial-contaminated samples O PCR primers may be (purely coincidentally) complementary to non-human DNA, so we do not know if the result is a copy of human DNA, so it is mixed with other primers and 2. PCR is either performed (human DNA) or not (foreign DNA) O it is determined whether the DNA sample belonged to a human or not - multiplex PCR - two or more PCRs take place in one reaction mixture at a time

Answer 46

- unknown mutation - complete analysis O sequencing - searching for the complete (exact) order of nucleotides in an amplified section of DNA - known mutation - targeted analysis O hybridization - We analyze the PCR product using a labeled probe § nucleotide linkage based on complementarity = hybridization § the DNA fragment is placed in a tube together with the labeled probe, which is complementary to a healthy part of the gene, if there is a mutation then the fragment does not associate with the probe O restriction fragment length polymorphism (RFLP) § The PCR product is specifically digested with restriction enzymes ( restriction endonuclease - restrictase) § the endonuclease recognizes and cleaves them in a specific sequence (eg ... CCAAGG ... -> ... CCA and AGG ...) § Inspired by bacterial enzymes, enzymes can now be made to order in laboratories as required § the cleavage result is suitable for gel electrophoresis

Answer 47

- the process by which genetic information stored in individual genes is realized as functional molecules of encoded proteins (ie the transfer of genetic information from DNA -> RNA -> protein) - the expression of individual genes is regulated in cells => cells can quickly adapt to changes in the environment - cell differentiation - expression of different genes leads to different cell types

Answer 48

1) genome (DNA) 2) transcription (DNA -> RNA / primary transcript) 3) posttranscriptional modifications (RNA / primary transcript -> mRNA) 4) mRNA 5) translation (mRNA -> polypeptide chain) 6) post-translational modifications (polypeptide chain -> functional protein) 7) protein degradation (functional protein -> degraded protein)

Answer 49

- gene amplification - the number of copies of one gene will increase -> transcription will overwrite it more -> expression will increase - genome rearrangement - the genome is not 100% stable, eg transposons (semiparasitic segments of DNA capable of changing their position and replicating in the genome) or genes encoding immunoglobulins - chromosome condensation / decondensation - transcription factors and RNA polymerase need developed DNA to work -> heterochromatin or barr body are not expressed O histone deacetylase - cleaves the acetyl group from the histone to condense the DNA - DNA methylation - higher degree of methylation -> lower degree of gene expression O in general, genes with methylated DNA are not expressed (Barr body, imprinting) O methylase - catalyzes the methylation of cytosine at 5'C in DNA (5-methylcytosine) O methylation is also a mechanism of gene imprinting

Answer 50

- is regulated by proteins that bind to regulatory DNA sequences - DNA regulatory sequences - 10-10,000bp long sequences that are involved in turning specific genes on and off O important regulatory sequences - promoters and enhancers (special DNA sequences capable of triggering transcription-specific gene, even at a distance of up to 1,000,000bp) - proteins regulating gene transcription O general transcription factors - ubiquitous, attached to everything O specific transcription factors - genes also have their own transcription factors, they are the main regulators O they contain several DNA binding motifs § homeodomain - has 3 α-helix parts -zinc finger- a zinc atom is attached here - leucine zipper- contains a lot of leucine

Answer 51

- general transcription factors - they associate with RNA polymerase at the promoter via binding to the TATA box - TATA box - a DNA sequence on a promoter that usually contains nucleotides A and T - activator and enhancer - the activator binds to the enhancer, together through mediator proteins, and general transcription factors help to bind RNA polymerase to the promoter and trigger transcription O the activator and enhancer need not be at all near the transcribed gene - combinatorial control - Several protein regulators work together to regulate the expression of a particular gene - many of these regulators are needed for activation

Answer 52

O operon - a set of genes transcribed from a single promoter O operator - a site on the promoter where the protein can bind and function as transcriptional repressor / activator O repressor operon - trp operon - if there is too much tryptophan, it mounts the operator and blocks further synthesis O activator operon - lac operon - if there is too much lactose, it mounts the operator and activates the synthesis of the enzyme, which can metabolize lactose

Answer 53

- RNA capping and RNA polyadenylation (increase mRNA stability) - post-transcriptional modifications affecting gene expression O alternative montage - allows the coding of several genes with the same gene, thanks to the use of other combinations of exons of that one RNA itself (exons may be omitted, but their order must be maintained) § different cell types make different proteins from the same gene O RNA editing - after transcription, nucleotides in the transcribed RNA can be inserted, deleted or substituted § modification of transcribed genetic information - discovery of new initiation and stop codons , associated with a change in reading frame

Answer 54

- mRNA degradation - mRNA viability affects expression ( the more stable the higher the expression level) - microRNA - short regulatory RNAs that regulate gene expression by regulating the degradation of the respective mRNA O it looks for complementary sections of RNA as soon as it finds such a section it sits down and begins to degrade the whole fiber - mRNA viability can also be regulated by nucleotide sequences in the 3 ́ untranslated region of the mRNA e.g. IRE (iron responsive element) , to which it is bound IRP (iron regulatory protein)

Answer 55

- it can be regulated by the binding of a specific protein to untranslated sections of mRNA - e.g. IRE in the untranslated 5 'region of the mRNA , to which it is bound IRP and translation is blocked

Answer 56

- Post-translational modifications of a polypeptide chain involve a number of mechanisms, including chain cleavage and molecular binding - a) removing methionine from the N-terminus - b) removing the signal sequence ( which determines the target of the protein) - c) proteolytic cleavage - forming a functional protein by cleaving the precursor polypeptide chain O proinsulin -> insulin + C peptide - d) forming disulfide bridges - they form between adjacent cysteines, they stabilize the structure of the protein - e) chemical modification of amino acids - phosphorylation (phosphate-binding) and hydroxylation (OH binding) O only tyrosine, serine, histidine, and threonine can be phosphorylated - f) glycosylation - binding of the oligosaccharide chain, glycoproteins are formed in this way (this is not possible in bacteria) - g) bonding of a prosthetic group - non-amino acid / non-protein molecule required for protein function (heme)

Answer 57

- a method of regulating the concentration of a particular protein in a cell - proteasome - a large complex of proteolytic enzymes arranged in a cylindrical shape with a catalytic site inside - ubiquitin - a small protein, covalently attached to proteins, indicates them for degradation

Answer 58

Gametes are germ cells - gametogenesis - differentiation of highly specialized germ cells capable of creating a new individual after fertilization - egg (ovum) - various sizes, carries a lot of nutrients - sperm - small, motile

Answer 59

- germ cells can be recognized very early in the embryo O they can be seen for the first time in the yolk sac of the embryo around the 24th day of development - 4. -6. week they migrate through the mesenchyme to the places where the gonads should form - after migration, germ cells (which have multiplied along the way) induce genital development - oogony - from several thousand, mitosis multiplies to + - 7 million (roughly during the 2nd - 5th month of development) O around the 7th month, oogonia ceases to multiply and enters the prophase of the first meiotic division - spermatogony - they enter meiosis only during puberty and never lose the ability of mitosis

Answer 60

- the process that leads from spermatogonia to sperm - 3 phases - multiplication (mitotic division), maturation (meiosis) and differentiation - It takes about 9 weeks + a few weeks after the sperm are in the epididymis before they are able to function - the onset of sperm development takes place in the seminiferous tubules of the testis O seed-forming channels contain germinal epithelium - they pass through the entire height of the epithelium Sertolli cells, among which sperm occur at various stages of development § Sertolli cells help with differentiation and supply them with the necessary nutrients § stem cells sit on the basement membrane and divide mitotically § the cells gradually differentiate towards the lumen - among the seminiferous tubules are Leydig cells, which produce testosterone

Answer 61

- stem cells (spermatogonia), which attach to the basement membrane, divide mitotically, giving rise to spermatogonia A and spermatogonia B O spermatogonia - remain at the basement membrane, acts as stem cell O spermatogonia B - already further they do not divide mitotically O penetrates the barrier that holds spermatogonia A in place and becomes the primary spermatocyte - primary spermatocyte - meiotic division begins at puberty, but gets stuck in prophase I for a long time (3 weeks) O one primary spermatocyte divides into two secondary spermatocytes - secondary spermatocytes - it is further divided into 4 spermatids - spermatids (spermatozoa) - get rid of unnecessary organelles and begin spermiogenesis

Answer 62

- the process of maturation of spermatids in sperm - some organelles are transformed, others are depleted by the cell O chromatin it concentrates in the nucleus (heterochromatin) and moves to one side of the cell - it forms a header O Golgi apparatus turns into acrosome - the organelle that surrounds the front of the nucleus forms such a cap § It is full of enzymes that help sperm penetrate the egg O microtubules and dynein they begin to form an axoneme - a microtubule structure inside the flagellum O centrioles - one serves as an anchor for the flagellum, the other gives the material to form the axonema O mitochondria they begin to move to MT and surround them - the so-called mitochondrial helix ( they supply whip energy for movement) O everything else (including the cytoplasm) is thrown out of the cell in the form of residual bodies that phagocytose the surrounding Sertoli cells

Answer 63

- newly formed sperm ripen in the epididymis O sperm are formed, which, however, are still not able to fertilize - the so-called capacitance - capacitance - the final stage of maturation - preparation for the release of enzymes from the acrosome + changes in the sperm membrane O takes place only in the female reproductive system - sperm hyperactivation - increase in sperm movement - acrosomal reactions - fusion of the acrosome with the plasma membrane, formation of an acrosomal process

Answer 64

- supporting cells - provide a microenvironment for spermatogenesis - are anchored in the basal lamina - they have an oval core, a distinct nucleus - Neighboring Sertoli cells are connected by a tight junciton, forming hemotesticular barrier O it divides the epithelium into basal compartment ( spermatogonia A) an adluminal compartment ( residue) O it also has immunological significance - germ cells in the spermatocyte stage are genetically different from wear cells and they could be recognized as foreign and discarded by autoimmune processes O function of the selective transport mechanism

Answer 65

- are placed in groups between the testicular canals near the capillaries - produce androgens - testosterone - contain fat droplets, rich smooth endoplasmic reticulum and tubular type mitochondria

Answer 66

- at birth - 400,000 oocytes are surrounded by a layer of follicular cells O only about 400 of them mature, the rest degenerate - closely related to the ovarian cycle (controlled by the hypothalamic-pituitary system) - in addition to the development of the egg, the follicle (shell) around the egg also develops

Answer 67

- forms the stores of yolk as a reservoir of energy, phospholipids and cholesterol to build the membranes of the embryo - The adult egg is the largest cell in the body - contains a lot of proteins - other energy stores, transcription factors, signaling molecules - ribosomes and tRNA - proteosynthesis after fertilization - mRNA - early development - morphogenetic factors (transcription and growth factors) - It moves through lashes and muscle contractions - saved in cumulus oophorus

Answer 68

- zona pellucida - a lot of glycoproteins, GAGs, hyaluronic acids etc. O produced by the oocyte as a shield through which nothing passes O it only has a sperm receptor O after fertilization, the chemical composition changes - corona radiata - packaging made of follicular cells O connection to the oocyte using nexus

Answer 69

- primordial follicle - single-layer flat epithelium just below the surface of the ovary, diameter up to 40 μm O resting stage of the egg - primary follicle - monolayer cubic epithelium, diameter up to 100 μm O zona pellucida forms between the oocyte and the follicle - secondary follicle - multilayered epithelium, diameter 200 μm O oocyte enlargement, stromal cells line up circularly around the follicle (theca folliculi) - tertiary follicle = Graafian follicle diameter up to 2.5 cm O oocyte enveloped by a thick zona pellucida O theca folliculi divided into theca interna (epithelial cells) and theca externa (myofibroblasts) - yellow body - corpus luteum - what is left when Graaf's follicle bursts and the oocyte gets out - atresia - death of follicles

Answer 70

- rupture of the mature Graafian follicle - a sharp rise in LH concentration in the blood - the oocyte completes the 1st maturation division and enters the 2nd maturation division (stops in metaphase - the division is completed only after fertilization of the oocyte) → mature Graafian follicle bursts and empties (theca externa myofibroblasts) → the oocyte is captured by the fallopian tube, where it remains until becoming fertilized (approximately 3 to 4 days; if the oocyte is not fertilized, the 2nd maturation division is not completed and the oocyte is expelled from the body) O the movement of the egg in the fallopian tube is ensured by the movement of the cilia and the contraction of the muscle of the fallopian tubes

Answer 71

- the rest of the Graafian follicle that remains in the ovary gives rise yellow body - follicular cells are transformed into granulosal lutein cells and theca foliculi cells are transformed into theca-lutein cells O granulosa-lutein (large lutein) cells - they secrete gestagen, which induces reproductive tissue differentiation system and maintains pregnancy O theca-lutein (small lutein) cells - they secrete androgens - the corpus luteum is formed at the LH signal (= first signal; promotes progesterone production) - the corpuscle is then itself functional for about 12-14 days -> when the egg is not fertilized, luteolysis occurs - a scar remains = corpus albicans - fertilization → embryo produces hCG ( one of the markers of pregnancy tests) = the second signal for the corpus luteum to produce progesterone (massively mainly in the first two months) and grow strongly (corpus luteum graviditatis) - it produces only progesterone, not estradiol because it has no aromatase

Answer 72

- desquamation phase ( menstrual phase) - the pars functionalis breaks down, the blood vessels open - proliferation phase = follicular - growth of new epithelium from the remnants of glands, the mucosa grows rapidly, under the influence of FSH - secretory phase - The endometrium is the thickest, the endometrial glands are filled with secretions and twists glycogen, proteins, strom are stored in stromal cells. - eggs are capable of transcription even during meiotic division

Answer 73

- it most often takes place in the ampular section of the fallopian tube - approx. 24 hours: penetration of sperm into the oocyte -> completion of the 2nd maturation division -> connection of maternal and paternal chromosomes in -> formation of diploid zygote -> first mitotic division

Answer 74

- sperm must get through the corona radiata and the zona pellucida → in the zona pellucida, the sperm binds to its receptor (ZP3) and triggers acrosome response ( release of enzymes from the acrosome) → this creates channels through which sperm can penetrate - the cytoplasmic membrane at the sperm head merges with the oocyte membrane - the fusion of the membranes initiates a cortical reaction that prevents other sperm from entering the egg - during fertilization, the entire content of sperm enters the egg (the cytoplasmic membrane remains outside - it merges with the membrane of the egg) → part of the content is used by the egg for its own use (centriole + chromosomes), the rest is destroyed - imprinting - disabling some genes depending on whether they are from the mother or the father; important for the differentiation of the embryoblast into the trophoblast (in the father, the genes for the embryoblast are turned off so that only those on the trophoblast are affected and vice versa)

Answer 75

- completes the 2nd maturation division (a mature oocyte and a secondary pole body are formed) - chromosomes are enveloped by a nuclear envelope - maternal primordial nucleus - the sperm nucleus is decondensed and its nuclear envelope is renewed - paternal primordial nucleus - followed by the approach of both primordial nuclei → decay of nuclear envelopes → chromosomes are captured on a common dividing spindle → diploid zygote - the rest of the sperm is destroyed by zygote enzymes

Answer 76

- rapid blockage of polyspermia - change in electric potential (Ca 2+) - slow blockage of polyspermia - enzymes from cortical granules prevent the binding of any other sperm by destroying other binding sites in the zona pellucida (ZP2 and ZP3) - fertilization envelope - space between pellucida and egg - GAG, peroxidase and hyaline - zonal reaction - leaching of hydrolytic enzymes from the oocyte, takes place in the zona pellucida

Answer 77

- the restoration of diploid chromosome number (new combination of genetic information) - gender is determined - initiation of scoring (development of a new individual) - sperm contributed to this by a mitotic spindle

Answer 78

- it is a mitotic division without cell growth and proteosynthesis - the number of cells increases without increasing the volume / size of the whole embryo O the cells divide mitotically without synthesizing new organelles after mitosis - mitotic division is equal and total O 40 hours - 4 cells O 3ED - 6-12 cells O 4ED - 16-32 cells - this stage of development is called morula

Answer 79

Differentiation: process of generating diverse types of cells (cell specialization) zygote → more than 200 distinct cell types in vertebrates

Answer 80

Determination: process in which the cell becomes commited to certain fate Cell usually becomes determinated before it starts to differentiate.

Answer 81

* Development (ontogenesis) of a multicellular organism * Renewal of tissues and organs Development (ontogenesis) of multicellular organism: zygote → mature organism Ontogenesis is realized in coordination with cell proliferation. Renewal of tissues & organs: * Physiological cell renewal * Repair: repair regeneration wound healing

Answer 82

The genome remains intact during differentiation. Different cells of organisms do not contain different genes but they express different genes. Cell memory: cells differentiate and remain differentiated after the signal for differentiation disappears. Cells keep in their memory the effects of past signals and pass them on to their descendants. Mechanisms of cell memory: positive feedback (self-activation of gene expression) * Positional information: cell is capable of retaining information reflecting its location in an organism.

Answer 83

* Totipotence: cells of early stages of cleavage * Pluripotence: stem cells (blood cells) * Unipotence: stem cells (epidermis)

Answer 84

Signaling molecules are involved in the regulation of cell differentiation during development. Morphogen (signaling molecule): concentration gradient of a morphogen forms positional signal for individual cells → relevant differentiation

Answer 85

* Asymmetry: chemical and other asymmetries of the egg →cleavage results in cell with different quantities of determinative molecules * Embryonic induction: interaction of cells → certain fate of one or both participants * Positional signal: formation of concentration gradient of signaling molecule (morphogen) → positional signal for cells * Response timing: cells change their internal status during the time (intracellular clock) → they respond differently to the same signal during different time periods

Answer 86

Homeotic genes: they determinate anteroposterior character of Drosophila body segments Homeotic genes are organized within Hom complex in one chromosome. Hox genes: in vertebrates homologous with homeotic genes of Drosophila Hox genes are organized within Hox complexes. Hox complexes: 4 Hox complexes in mammals (Hox A, Hox B, Hox C, Hox D) individual Hox complexes are localized on different chromosomes Hox complexes are involved in generation of positional information (positional signal): proteins coded by individual Hox genes function as molecular markers of a body region. The sequence of genes within chromosome corresponds with the spacial sequence of expression of genes within body

Answer 87

Cell senescence: cell after a certain number of realized cell divisions is losing its ability to proliferate and finally it inevitably dies (state of terminal differentiation) Biological significance of cell senescence: protection against uncontrolled proliferation Genetic control of cell senescence

Answer 88

The life span of the cell is not determined by certain time but by certain number of realized cell cycles. Hayflick limit: programmed life span of somatic cell of certain organism expressed as a number of cell cycles Hayflick limit of human embryonic cells: 50 cell cycles Immortality of cells: cancer cells cells of germinal lines

Answer 89

* Accumulation of mutations and injuries: wear-and-tear theory * Oxidative damage * Damage of mitochondrial genome * Role of insulin signaling: inhibition of the expression of proteins protecting against injuries * Shorterning of telomeres

Answer 90

Production of ROS (reactive oxygen spiecies): result of metabolism ROS, on the basis of oxidation, they damage membranes, proteins and nucleic acids.

Answer 91

Mutation rate in mitochondrial DNA is significantly higher (10-20x) than mutation rate in nuclear DNA. Damage of mitochondrial genome: defects in energy production ROS production apoptosis induction

Answer 92

Mechanism of telomere shortering: insufficient function of telomerase Consequences of telomere shortering: DNA damage → p53 activation

Answer 93

Programmed cell death: cell has genetically encoded program for selfdestruction, after receiving relevant signal the cell is active participant of selfdestruction Apoptosis: type of programmed cell death in animals (characterized by caspase activation) it is accomplished under physiological conditions Necrosis: nonprogrammed cell death necrosis is accomplished under nonphysiological conditions it results from irreversible cell damage

Answer 94

* Necroptosis (necrosome, permeabilization of plasma membrane) * Lysosomal cell death (permeabilization of lysosomal membrane) * Pyroptosis (inflammasome: activation of caspase-1) * Ferroptosis (iron accumulation, lipid peroxidation, permeabilization of plasma membrane) * Autophagic cell death (autophagy/autophagosome)

Answer 95

Apoptosis * active process (it requires energy supply) * early DNA degradation * chromatin condensation * plasma membrane stays intact * cell shrinking * formation of apoptotic bodies * without an inflammatory response Necrosis * passive process * DNA stays intact * chromatin stays intact * loss of function and integrity of plasma membrane * cell swelling * disintegration of plasma membrane → cell lysis * accompanied by inflammatory response

Answer 96

* Regulation of cell number * Formation of organisms during development * Function of the immune system * Pathological states

Answer 97

Cell elimination: cells with damaged DNA, virally infected cells * Maintenance of tissue homeostasis: maintenance of steady state cell number Tissue homeostasis: balance between the production of new cells by proliferation and loss of cells by apoptosis

Answer 98

* Sculpting of tissues/organs: formation of fingers, formation of cavities * Elimination of tissues/organs: frog tail, male oviduct (Müllerian duct), excessive neurons * Atrophy of tissues/organs

Answer 99

* Negative selection of B & T cells * Mutual elimination of activated T lymphocytes * Protection of cells of tissues with immune privilege

Answer 100

Tumor diseases: development of tumors (deregulation of apoptosis) therapy of tumor diseases * Diseases associated with apoptosis: Alzheimer´s disease, cardiac infarct

Answer 101

Activation of executioner caspases (proteases) represents the key event of initiation of apoptosis execution. Activated executioner caspases cleave death substrates → apoptosis execution

Answer 102

Caspases: cysteine proteases (active cysteine residue is required for proteolytic activity, they cleave substrates at the place of aspartic acid residue) 3 functional groups of caspases: * Initiator caspases * Executioner caspases * Inflammatory caspases (e.g. caspase-1)

Answer 103

activated within the framework of relevant activation caspase-9 (apoptosome), caspase-8 (DISC complex), caspase-2

Answer 104

activated by initiator caspases they cleave death substrates caspase-3, caspase-6, caspase-7 Initiator caspases → executioner caspases → death substrates

Answer 105

Cleavage of death substrates by executioner caspases → execution of apoptosis Death substrates: * DNA fragmentation: CAD (caspase-activated DNase)/iCAD (inhibitor of CAD), DNA ladder * DNA repair: PARP [poly (ADP-ribose) polymerase] * Structural proteins: cytoskeletal proteins (lamins, actin) * Regulatory proteins: Rb protein induced changes in the nucleus, cytoplasm, and plasma membrane (translocation of membrane phosphatidylserine)

Answer 106

Apoptotic signals: * Endogenous apoptotic signals: p53 activation * Exogenous apoptotic signals: apoptotic signaling molecules

Answer 107

* Mechanisms of p53 activation: DNA damage, hypoxia etc. * Activated p53 functions as a transcription factor. Genes induced by activated p53: * mdm2 (feedback regulation of p53 activity) * p21 gene (inhibitor of CDK 2 → cell cycle block) * bax (proapoptotic protein of Bcl-2 family → apoptosis) * IGF-BP3 gene (insulin-like growth factor-binding protein 3 blocks IGF-I activity)

Answer 108

DNA DAMAGE ↓ p53 ACTIVATION ↓ Bax EXPRESSION ↓ Bax/Bax CHANNELS IN MITOCHONDRIAL MEMBRANE ↓ CYTOCHROME C RELEASE FROM MITOCHONDRIA ↓ APOPTOSOME FORMATION ↓ CASPASE-9 ACTIVATION ↓ CASPASE-3 ACTIVATION ↓ APOPTOSIS

Answer 109

* Glucocorticoids * Cytokines (viability factors) * Ligands of death domain receptors * Granzyme B

Answer 110

Apoptosis induction by glucocorticoids: regulation of the expression (induction) of proapopottic proteins Bcl-2 family (Bax) → apoptosis induction * cortisol

Answer 111

Deficit of some cytokines leads to apoptosis induction: viability factors Inhibition of apoptosis by viability factors: regulation of the activity (inhibition) of proapoptotic proteins of Bcl-2 family (Bad) * Viability factors: IGF-I, IL-3, IL-4, IL-6, GM-CSF

Answer 112

Apoptosis induction by ligands of death domain receptors: ligand interaction (extracellular signaling molecules) with relevant membrane receptor generates intracellular apoptotic signal → apoptosis induction via death receptor pathway Receptors with death domain and their ligands: * Fas receptor (Fas): Fas ligand * TNFR1 (tumor necrosis factor receptor 1): TNF Interaction of Fas ligand with Fas receptor represents main mechanism of apoptosis induction in immune system (cytotoxic T lymphocytes, NK cells).

Answer 113

Apoptosis induction by granzyme B: synergistic action of secreted perforin and granzyme B * Perforin: it forms channels in plasma membrane for granzyme B entrance * Granzyme B: protease, caspase activation System perforin/granzyme B is involved in immune system (cytotoxic T lymfocytes, NK cells).

Answer 114

Proteins of Bcl-2 family: characteristic BH (Bcl-2 homology) domain TM (transmembrane) domain [FIG.] Antiapoptotic vs. proapoptotic proteins of Bcl-2 family * Bcl-2 subfamily (antiapoptotic): Bcl-2, Bcl-xL * Bax (BH123) subfamily (proapoptotic): Bax, Bak * BH3-only subfamily (proapoptotic): Bad, Bid, Puma Proteins of Bcl-2 family form homodimers and heterodimers by means of their BH domain. Mutual ratio of antiapoptotic and proapoptotic proteins of Bcl-2 family decides as to apoptosis induction. Role of proteins of Bcl-2 family in regulation of apoptosis is evolutionary conserved.

Answer 115

Mechanisms of apoptosis induction lead to the activation of initiator caspases and subsequently to the activation of executioner caspases. Executioner caspases carry out, on the basis of cleavage of death substrates, apoptosis (apoptosis execution). Activation of caspases: on the basis of proteolytic cleavage Basic pathways of caspase activation: * Death receptor pathway * Mitochondrial pathway

Answer 116

Death receptor pathway (extrinsic pathway): * Ligand (signaling molecule) ↓ * Receptor with death domain ↓ * Formation of DISC complex (death domain of the receptor, adaptor protein(s), procaspase-8) ↓ * Activation of caspase-8 (initiator caspase) ↓ * Activation of caspase-3 (executioner caspase) ↓ * Cleavage of death substrates (apoptosis execution)

Answer 117

* Mitochondrial pathway (intrinsic pathway): * Bax (proapoptotic protein of Bcl-2 family) ↓ * Bax/bax channels in mitochondrial membrane ↓ * Release of cytochrome c ↓ * Formation of apoptosome (cytochrome c, Apaf-1, procaspase 9) ↓ * Activation of caspase-9 (initiator caspase) ↓ * Activation of caspase-3 (executioner caspase) ↓ * Cleavage of death substrates (apoptosis execution)

Answer 118

- the first days of fertilized egg development take place zygote -> blastomera -> morula -> blastocyst - the cells formed by the first divisions are called blastomeres

Answer 119

- grooving takes 1-3 days and is equal and total O mitotic division without cell growth and proteosynthesis (so the number of cells increases, but the total volume remains the same) - the cells remain inside the zona pellucida ( glycoprotein envelope, formed during oogenesis) - by stage 8 blastomer, the cells are straight ( they are totipotent, a new individual can be formed from each cell) → another grooving division follows (approximately 3 days after fertilization) - 16 blastomeres are formed = morula ( the formation resembles a mulberry fruit - hence the name) -> at this point, the individual blastomeres begin to differ O morula - stage about 20-50 cells O set aside inner and outer cells / blastomers , § inner cells - connected by tight junctions and communicate with each other using nexus O internal cell mass, develops in embryo § outer cells - communication with the external environment, connected by tight junctions and connecting complexes O external cell mass, develops in trophoblast ( formation of amniotic sacs and placenta)

Answer 120

- from the 4th day of development it begins to form blastocyst cavity - fluid begins to enter the intercellular spaces between the embryoblast and trophoblast cells → a unit called blastocyst O the cells of the inner and outer cell mass begin to polarize across the board and form trophoblast ( outer meat) and embryoblast (inner meat) O embryoblast cells they are further divided, they are clustered together and determine embryonic pole ( the opposite is vegetative ) O trophoblast cells are flattened and all around on surface (resembling a single layer of flat epithelium) § trophoblast cells produce adhesive molecules O L-selectin - ensures adhesion to the uterine epithelium mucous membrane O integrins - laminin and fibronectin receptors - the blastocyst travels from the fallopian tube into the uterus - cells corona radiata gradually falls off from the egg (these are the cells around the zona pellucida, they nourish the egg)

Answer 121

- Day 5 - disruption of the zona pellucida (by trophoblast enzymes, sensitive period of the blastocyst, toxins cause death) - Day 5 - 6 - crack formation, blastocyst penetrates out (hatching) - Day 6 - first contact of the blastocyst (embryonic pole) and the uterine mucosa (zona functionalis) and subsequent egg ingrowth - trophoblast cells in direct contact with the epithelium divide much faster and the trophoblast begins to divide O syncytiotrophoblast - daughter cells of rapidly dividing cells, coalesce together to form a multinucleated cell, which gradually envelops the entire blastocyst O cytotrophoblast - original trophoblast, cubic cells - proper implantation takes place in the body of the uterus, most often in the upper part

Answer 122

- syncytiotrophoblast produces metalloproteinases (= proteolytic enzymes, that help to penetrate further into the uterine mucosa) and chorionic gonadotropin ( hCG), which stops the menstrual cycle ( the lining of the uterus is maintained in the secretory phase throughout pregnancy) and maintains increased progesterone production O the first signal for progesterone production is LH, whose level gradually begins to decline → for progesterone to be still produced, a second signal is needed = hCG (this hormone works very similar to LH) - progesterone in endometrial cells subsequently induces the so-called decidual reaction = secretory cells in the uterine lining begin produce uterine secretions and begin accumulate glycogen and lipids → glycogen and lipid stores are the primary source of nutrition for the implanting embryo O the lining of the uterus is called at the end of the secretory phase and throughout pregnancy decidua and is formed decimal cells § the whole decidua consists of several parts → decidua basalis ( forms the placenta), decidua marginalis (creates the edges of the placenta), decidua capsularis a parietalis ( create fruit wrappers)

Answer 123

- the embryoblast divides into two layers ( the so-called bilaminar embryonic disc): O hypoblast - from embryoblast cells that target the blastocyst cavity (they are cubic) O epiblast - from other embryoblast cells (they are cylindrical) - between the epiblast and the cytotrophoblast, a cavity, which is called, soon begins to form the amniotic cavity - cells from the hypoblast they begin to migrate gradually and create thin membrane, which covers the entire interior of the cytotrophoblast O this membrane is called exocoelom membrane, or also Heuser's membrane - The exocoelom membrane together with the hypoblast form the so-called primitive yolk sac O the primitive yolk sac has the same functions as the secondary yolk sac → it is mainly different metabolic functions ( nutrition, hematopoiesis, nutrient metabolism...)

Answer 124

- implantation is completed, when at the site of blastocyst entry into the endometrium a fibrin plug is formed - in syncytiotrophoblast from the 8th day onwards, small cavities are formed, which are called lakuny - during the 12th day the lacunaas stop growing, they begin to coalesce, and form a network of interconnected cavities - proteolytic enzymes of the syncytiotrophoblast begin to erode capillaries (red in the picture) → blood is poured from the capillaries into the lacuna network and the embryo can diffuse to receive gases and metabolites from the mother's blood (mother's and embryo's blood is never mixed under normal circumstances -> this can occur during abortion , childbirth...) - blastocyst obtained nutrients from uterine gland secretion during implantation (before termination) = histiotrophe

Answer 125

- syncytiotrophoblast and cytotrophoblast grow faster than hypoblast and epiblast → as a result, between the inner side of the trophoblast and the outer side of the primitive yolk sac a cavity with a new cell population, known as extraembryonic mesoderm appears - in the extraembryonic mesoderm, large cavities soon begin to form, which join together to form one large so-called chorionic cavity - chorion = extraembryonic mesoderm, cytotrophoblast and syncytiotrophoblast O chorion can be divided into two parts → chorion frondosum and chorion laeve § chorion frondosum - grows and expands at the embryonic pole villi, which subsequently participates in the creation of placenta → is in this area decidua basalis § chorion laeve - at the abembryonic pole, the villi gradually degenerate; creates fruit packaging → is in this area decidua capsularis

Answer 126

- around day 13, a part of the primitive yolk sac is split off, and a smaller, secondary yolk sac is formed by migration of other hypoblast cells along the Heuser membrane - the chorionic cavity continues to enlarge and eventually completely separates from the cytotrophoblast, except for a short strand of extraembryonic mesodermal cells - this strand is called germ stem ( future umbilical cord) - the cleaved remnant of the primary yolk sac disappears over time - the secondary yolk sac forms blood (hemopoiesis), forms blood vessels, serum proteins, metabolizes nutrients, and serves as a storehouse of germ cells - the organ for providing nutrition is the chorion / placenta, it needs the vascular system and contact with maternal blood

Answer 127

- the immune system treats the uterine lining differently - it reduces immune responses and thus maintains a special environment for the embryo O in addition, the embryo has almost no antigens - progesterone reduces the non - specific immune response (complement) and interleukin-2 reduces the specific response - both the syncytiotrophoblast and the cytotrophoblast do not express common antigens (or are overlapped) form a barrier between maternal and fetal tissue (there must be no direct contact between maternal and fetal blood) - cytotrophoblast envelope - cytotrophoblast cells penetrate the villi and form a barrier between maternal and fetal tissue

Answer 128

- part of the chorion (frondosum) helps with the development of the placenta and part (laeve) with the development of the amniotic sac - The placenta is a fetal organ that provides prenatal nutrition and a variety of other functions O metabolism - eg glycogen synthesis O transport of gases and nutrients O excretion of metabolic waste products O hormone production ( chorionic gonadotropin) - in the middle of the 2nd week the buds of the cytotrophoblast grow into the syncytiotrophoblast -> they form primary chorionic villi O at the end of the 2nd week, the mesoderm also intervenes in the buds -> secondary chorionic villi O at the end of the 3rd week, blood vessels begin to form in them -> tertiary chorionic villi ( definitive) - The placenta is actually formed by the cooperation of maternal and fetal cells O fetal part of the placenta - chorionic villi + chorionic plate (extraembryonic mesoderm ligament) O maternal part of the placenta - endometrium (pars functionalis) + decidua basalis O between these parts is the so-called intervillous space (filled with maternal blood) - Insufficient vascular supply of the placenta caused by poor reconstruction of the spiral arteries may be responsible for intrauterine growth retardation of the embryo - The umbilical cord contains two arteries and one umbilical vein

Answer 129

- transfer of respiratory gases, metabolites, electrolytes and maternally derived antibodies (IgG) - production of hormones - progesterone, estriol, chorionic gonadotropin, somatomammotropin (placental lactogen)

Answer 130

- what is transmitted O metabolites - glucose, amino acids, fatty acids, water, vitamins, electrolytes O hormones - unconjugated steroids only O maternal antibodies, transferrin + iron ( for erythrocytes) O drugs - how it is transmitted - diffusion, facilitated diffusion, active transport, pinocytosis, bacteria can also own activity O in case of placental damage and other mechanisms (direct blood mixing, infections)

Answer 131

- Ectopic implantation ( extrauterine implantation) - mostly in fallopian tubes (95%, rather ampoules than insterstium), ovaries, uterine horn or abdominal cavity (in the so-called Douglas space - behind the uterus, sometimes some fluid may get there) O All of these pregnancies are life threatening - placenta praevia - the placenta forms too low and grows over the cervix -> it clogs the child's birth canal and the child suffocates - the three pathological conditions in which the placenta penetrates deeper than normal differ in depth O placenta accreta - the placenta attaches to the myometrium O placenta increta - the placenta penetrates through the myometrium O percenta placenta - the placenta grows throughout the uterus and attaches to something in the abdomen - preeclampsia - serious illness O primary symptoms of edema, proteinuria and hypertension , from which vasoconstriction, hormonal imbalance, convulsions, dehydration, ischemia, liver necrosis, hematomas, placental infarction O The condition of a woman with preeclampsia is monitored very carefully, all symptoms are treated consistently and a doctor is always ready to terminate a pregnancy (which cures preeclampsia)

Answer 132

- lots of types O dizygotic - fertilization of two eggs O monozygotic - fertilization of one egg, depending on the time of division may have common organs, the simplest the complication is a common placenta, then there may be more serious monozygotic twins § dichorionic - each has its own chorion § monochorionic - common chorion * diamniotic - each has its own amnion * monoamniotic - common amnion O Siamese twins - some things common even after birth

Answer 133

prechordal plate (14D) beginning of week 3 - a lot of crucial and most important processes happening at once! formation of the primitive streak formation of notochord formation of 3 embryonic layers —> GASTRULATION

Answer 134

- after the formation of the secondary yolk sac and the embryonic stem at the end of the 2nd week, the next developmental stages of the embryo come into play → gastrulation, notogenesis, somitogenesis and neurulation ( 3rd - 4th week, some of these processes take place at the same time)

Answer 135

- the process of differentiation of the bilaminar disc (epiblast + hypoblast) into three germ layers - ectoderm, mesoderm and entoderm - begins at the beginning of the third week of creation primitive stripe, which leads from one side to the middle of the epiblast O this strip runs through the center and identifies the cranial (head) and caudal (tail) sides

Answer 136

- it arises first primitive (Hensen's) node (= hole in the epiblast) → the node contains a circular depression = primitive hole → this hole begins to expand caudally in the form of the so-called primitive furrows, which stretches along the entire length of the resulting primitive stripe ( cranial extension of the primitive stripe = primitive node - see picture)

Answer 137

- During gastrulation, two specific membranes are gradually formed, according to which it is also possible to distinguish the cranial and caudal side → the cranial side is distinguished by oropharyngeal membranes ( in the figure it is shown as a small disk in the epiblast opposite the primitive node / strip; it arises from a prechord disc - see. further), the caudal side then according to cloacal membranes O a primitive band runs between these membranes - primitive stripe and node functions O regulation of proliferation, migration, differentiation, production of signaling molecules, expression of Hox genes and position determination, each segment is differentiated differently

Answer 138

- primitive node is basically an opening that is created so that the cells of the epiblast know where to go → they begin to sink into it and thus penetrate under the epiblast O the first cells, which pass through the primitive node and continue in the cranial direction, form the so-called prechordovou plate - extends from the primitive node primitive furrow, which extends caudally (towards the cloacal membrane) → through the furrow then other epiblastic cells migrate inwards → migrating epiblastic cells penetrate between the hypoblast cells and begin to gradually replace them, some also remain in the space between the original epiblast and hypoblast - hypoblast cells are subject apoptosis - cell migration is controlled by growth fibroblast factor 8 (FGF8), which is made up of cells primary strip O FGF8 directs migration by inhibiting the expression of the protein responsible for epiblast cell binding - E-cadherin - this process is called invagination

Answer 139

- hypoblast cells are constantly replaced by epiblast cells until they are completely replaced, resulting in definitive entoderm ( note entoderm and endoderm are synonyms) - around day 16, most of the hypoblast cells are replaced and the remaining epiblast cells are called ectoderm - some migrating epiblast cells do not replace hypoblast cells, instead they remain in the space between the ectoderm and the newly formed endoderm and thus form a new cell population - intraembryonic mesoderm - tight, specific ectoderm and entoderm contacts they can arise oropharyngeal membrane on the cranial side and cloacal membrane on the caudal side - after about the 4th week of development, the primitive strip undergoes degenerative changes and disappears and if this does not happen, it arises sacrococcygeal teratoma

Answer 140

notochord is a rod-shaped cell formation resulting from the transformation of the head process O delineates the axis of the embryo, gives it strength O serves as the basis for the development of the axial skeleton O indicates the next position of the vertebrae - notogenesis begins during gastrulation at about day 16 - in the newly emerging intraembryonic mesoderm a solid cord is formed - head protrusion ( the protrusion grows from the primitive node towards the prechordal disc, where its growth stops) → a lumen is formed in the axis of the head protrusion = notochord channel

Answer 141

O caudal regression syndrome - various developmental defects of the lower body - spine, spinal cord, sirenomelia ( leg connection) O sacrococcygeal teratoma - a huge solid tumor in the sacral area of the spine

Answer 142

- process induced by origin notochord - so-called neural induction - the formation of a notochord causes the thickening of cells in the cranial part of the ectoderm above the notochord → this formation formed by thickening is called neural plate - neuroectoderm ( its edges neural bar) O notochord produces various signaling molecules (eg Wnt, FGF, BMP), which cause this thickening neural tube ( when the tube is closed, apoptosis of the cells occurs at the point of contact of the ramparts) - the neural tube closes first in the middle of the embryo (cervical area), then widens on both sides from the center (cranial and caudal side) - the narrower lower part of the neural tube gives rise to the spinal cord, the wider upper part becomes the brain

Answer 143

- The segments of the brain part of the neural tube are called neuromers and are 3 (from top to bottom) O prosencephalon - end brain O mesencephalon - midbrain O rhombencephalon - brain stem

Answer 144

- takes place at the same time as neurulation - Somites can be imagined as precursors of the vertebrae, they are a pair of areas of the mesoderm, which lie on both sides of the neural tube and notochord, they can form the thorax, spine, spinal cord envelopes, muscles, cartilage, ligaments, back skin... - development begins within the 3rd week - as the primary strip recedes and neural ridges begin to form, the mesoderm around the notochord ( called paraaxial ) begins to clump into somite pre-stages, the so-called somitomer - because the notochord progresses from the cranial to the caudal part, so do somitomers

Answer 145

O sclerotoma - the ventral part, differentiation under the influence of Shh (produced by the notochord) condenses around the chord dorsal, the caudal half of the previous sclerotoma joins the cranial half of the next sclerotoma to form the vertebral body O myotome - the middle part of the original somite, forms the basis of the torso muscles O dermatome - dorsal part - disintegrates, forms the basis of the ligament and skin of the back

Answer 146

- Caudal morphogenetic system ( primitive node + primitive stripe) a cranial signaling center ( transitional plate) segment the mesoderm through the mechanism O molecular clock - cyclic production of Wnt and FGF signaling molecules + costimulation of RA and Notch O induce the formation of somites O regulate the expression of hox genes - the lateral part, which did not receive signals, will not be segmented - the so-called lateral disc - the concentration of morphogens in the mesoderm determines the dorso-ventral axis

Answer 147

- Week 3 - 8 - all basic organ systems will be created - at the end of the embryonic period, the embryo looks at least a little like a child, it grows from about 3 mm to about 30 mm - main critical period - in 3.-8. week teratogens have the greatest effect, causing the most serious defects

Answer 148

- Week 4, during neurulation, the neural tube grows faster than the rest of the embryo - the formation of folds takes place in the longitudinal and horizontal planes - horizontal axis O folds are formed at both ends of the embryo, the head and caudal eyelash, the anterior and posterior areas are formed embryos therefore move ventrally (forward, to the abdomen) O as a result of the disparity between the growth of the edges of the germinal leaves and the brain and spinal cord, the body wall closes O head fold - it is caused by overgrowth of the brain across the oropharyngeal membrane § perdicardial coelom ( future pericardial cavity), the base of the heart and the oropharyngeal membrane move ventrally § part of the yolk sac it is taken into the embryo as the so-called front intestine - the base of the pharynx and esophagus § septum transversum ( base of the diaphragm) moves caudally O caudal fold - it is caused by the growth of the distal sections of the neural tube § tail landscape grows above the cloacal membrane § part of the yolk sac is taken into the embryo as the so-called hindgut, the end part of which soon widens slightly to form a cloaca, the whole base of the bladder and rectum - horizontal axis - a lateral fold is formed on both sides of the embryo due to the rapid growth of the spinal cord and somites O part of the yolk The sac is taken up in the embryo and forms the so-called middle intestine O germ stem transforms into umbilical cord

Answer 149

- 3 main brain sacs O prosencephalon O mesencephalon O rhombencephalon - the retina is also formed from prosencephalon

Answer 150

- ectoderm - CNS, PNS, retina, epidermis, mammary glands, enamel - neural crest cells - ganglia, Schwann cells, melanocytes, adrenal medulla, cerebrospinal fluid, muscles + ligament + cartilage/bones of pharyngeal arches, C-cells of the thyroid gland, - mesoderm - ligament, cartilage, bones, muscles, blood vessels, kidneys, ovaries, testes, spleen, adrenal cortex, mesothelium (a thin layer of squamous epithelium that covers some body cavities) - endoderm - GIT, respiratory system, thyroid gland, parathyroid glands, thymus, pancreas, liver, bladder

Answer 151

- since the last menstruation - from conception - ultrasound O estimation based on the development of morphological characteristics O according to the length-width ratio ( largest in 3 and 4 weeks) § later the length from the crown to the coccyx - stages according to Carnegie - classification of 23 developmental stages of the embryo

Answer 152

-from the 9th week until delivery relative slowing of head growth O 3rd month - half the length of the body O 5th month - one-third of the length of the body O at birth - a quarter of the length of the body high growth rate, weight gain, eyelids open at the end of the fetal period IUGR (intrauterine growth retardation) - intrauterine growth retardation - disorder O most often caused by placental insufficiency or decreased uterine blood circulation border of viability - the limit of the fetus' ability to survive premature birth O Weeks 22-25 are referred to as the gray zone with an uncertain prognosis O it is generally stated that a child weighing at least 500g born prematurely in the 24th week is able to live without a disability

Answer 153

- 30,000 genes - it's quite a few genes, that's why alternative splicing is used (= one gene can be translated in several ways) O the signals are repeated during life, but the cell gradually changes, and thus responds to the same signal in different stages of their development differently - many genes are the same across all animals (eg human and porcine insulin look identical, so in the past it was also treated with porcine insulin) and the different result (human / mouse) is also given by how these genes interact - information for the beginning of development is found in the egg (mRNA, proteins) - imprinting ( mammals) -> due to imprinting, for example, cells are divided into embryoblast and trophoblast - epigenetic regulation - interactions between different tissues affect the expression of the whole cascade of genes -> first regulatory genes are expressed, which then induce the expression of "downstream" genes, which ultimately leads to cell differentiation O it depends not only on the specific genetic information, but also on who / how reads it O The cells must be in the right place at the right time during the development and get the right signal in the right amount § The development of a zygote in a child is an exact sequence of signals, the deviation means malformation O usually two epithelial structures or an epithelium and a mesenchyme react § eg the interaction of the epithelium and the mesenchyme - one produces a signaling molecule and the other responds to it

Answer 154

- induction = one cell population affects the development of another cell population Oif one tissue affects another tissue - induction , if two tissues interact with each other - reciprocal induction (development of kidneys, eyes) O the tissue must be prepared for the signal (have receptors) and responds only to specific information (signal molecule) - determination = the cell decides on some morphological process based on induction - usually this sequence looks like induction → determination → basic morphogenetic process (proliferation, apoptosis, migration, association) or differentiation - signaling molecules are used for induction ( morphogens) produced in tissues O signaling: binding of a signaling molecule to membrane receptor -> signal transduction to the nucleus -> expression of a specific gene O to express the gene and transfer its information to peptide structures first require specific transcription factors and mRNA - however, the undifferentiated cell does not yet have specific transcription factors and mRNA, so it must begin with them O a cell that already has some specific transcription factors or mRNA but not protein determined (it is clear what the cell will become -> it is working on its differentiation, but it is not finished yet - there is nothing to know on the outside) - signaling has specific rules that allow only the right cells to differentiate

Answer 155

- tissue level mechanisms: O proliferation, reduction (apoptosis), migration, association - cell level mechanisms: O restriction - determination - differentiation - any defect in development has its origin in a significant deviation of the function of morphogenetic systems and always manifests itself by disruption of basic morphogenetic processes

Answer 156

- allows the growth of the embryo in the prenatal period O cell cycle time increases during life -> the shortest is at the beginning of the development when grooving ( about 8 hours / cycle) § differentiated cells can stop their cell cycle (G0 phase) - it allows the number of cells to increase overall and / or is concentrated only on a specific cell population -> embryo shaping, heart septum formation, etc. - in adulthood, proliferation is maintained in all regenerating tissues ( in epithelia, hematopoietic tissue, immune system...) and allows replacement of old / damaged cells ( the total number remains the same) - proliferation is tightly regulated O growth factors ( eg insulin, IGF, VEGF, FGF and many more) O with specific signaling molecules ( Wnt, Shh) - fractals - during the formation of glands, the cells are distributed in the free space, then resemble the branches of a tree

Answer 157

- physiological process - during development, an excessive amount of cells is produced, which act as reserves ( if an error occurs in any cell / population), and by reduction, these excess cells are destroyed - in addition to excess cells, we also get rid of defective ones by apoptosis - in adulthood the number of cells should remain the same = apoptosis and proliferation must be in balance - apoptosis is triggered by a response to two types of signaling O internal - bad genome p53 triggers apoptosis O external - cells need a constant signal from surviving factors, , to stay alive (signal disappears => apoptosis) § during development, apoptosis is usually triggered by a lack of growth factors

Answer 158

O finger formation and proper organ shapes O removal of tissues and organs in the adult do not occur - spinal end, mesonephros, Muller or Wolff canal O disposal of excess cells - neurons and myoblasts, which does not form synapses O closing of pipes and spaces - neural tubes, body walls O formation of articular clefts

Answer 159

- relocation of individual cells or cell populations - passive migration - in the embryo, mitotic activity is increased at certain sites - so-called proliferation centers O the cells are extruded from its place as a result of proliferation in the proliferation center - active migration - the cells create their own locomotor (moving) apparatus and adhesive contacts O needed actin and focal adhesions - essentially a signaling pathway O integrin receptors transmit information to FAK (focal adhesion kinase,tyrosine kinase), the FAK then processes the information and provides a response O according to the concentration of growth and migration signaling molecules in the intercellular mass FAK decides whether the cell will multiply and grow or migrate O integrins act as receptors as well as attachment and their expression in the cell is a functional image of migration O during migration, the leading pole (with focal adhesions) is visible on the cell, which catches on the surface and the siding, which he pulls behind him - during migration, the cells respond to signals from the environment O chemotaxis - movement in the direction of the chemical gradient O cells have specific receptors to molecules of the intercellular mass - examples - migration of myoblasts to limb buds, migration of neural lamina cells, CNS development O unrelated to development -> but by chemotaxis some white blood cells travel for inflammation O development of intraembryonic mesderm - formation of a bottled cell during migration of cells from the epiblast

Answer 160

- joining individual cells into higher functional units, as a prerequisite for their differentiation or function - cadherins are expressed - cell adhesion molecule (CAM) and N-CAM (neural CAM) - cadherin expression ( intercellular junction proteins) is considered a functional image of the association - this is how skeletal muscles, neural networks and kidneys, for example, are formed O skeletal muscle development - myoblast -> lots of myoblasts -> fusion, a determined muscle cell is formed § when strengthening, new skeletal muscles are not formed, only the muscles that are already there are enlarged (hypertrophied)

Answer 161

- different gene expression leads to the synthesis of other proteins ( structural and functional) and thus a different morphology - cells vary in size, shape, morphology and function - based on the morphology, the functions of the cell can be guessed and sometimes vice versa - hematopoietic tissue - the formation of blood cells, their development takes place O pluripotent stem cells -> multipotent stem cells -> precursors -> immature blood cells -> mature blood cells

Answer 162

- signals affect entire cell populations - morphogenetic systems O caudal morphogenetic system ( primitive node + primitive stripe) and a cranial signaling center ( prechord plate) - both are formed in the 3rd week - by common signals these two systems segment (subdivide) the embryo in the space between them O AER (apical ectodermal strip) and ZPA (zone of polarizing activity) forms the limb bud

Answer 163

- of mesenchyme - AER secretes FGF (fibroblast growth factor) leading to mesenchymal cell proliferation - ZPA secretes Wnt and Shh (specific growth factors), which trigger the expression of HOX genes determining the development of axes and fingers and BMP (transforming growth factor beta) genes - together with apoptosis they take care of differentiation

Answer 164

- morphogens Wnt and Shh ( produced by notochord, which is the dorsal string) - concentration gradient of morphogens (Wnt and Shh, each has a maximum concentration on one side) affects the development of cells in the neural tube - the result is different development of cells in the ventral ( front) and dorsal ( rear) corners of the spinal cord - during neuroectoderm differentiation, neuronal precursors (neuroblasts) travel from the germ layer The mesenchyme forms supporting, trophic and filling cells (adipocytes, chondrocytes, smooth muscle cells)

Answer 165

- planar polarization - desktop resolution O all cells are oriented in the same direction and in one plane - the cell itself knows where has a front and where a back O To achieve this state, cells use several mechanisms: § expression of different proteins on opposite sides of the cell - this allows determination of the anteroposterior axis * protein 1 on the one hand and protein 2 on the other hand, such labeling § transmitting signaling molecules in one direction only § planar mascara - does not serve to move, it is a receptor of signaling molecules (it knows from which direction the signal is coming) - default repression (costimulation) O one signal is not enough to transmit information -> usually cooperation of two ligands - eg FGF and Shh § local activator , which activates the receptor § signal molecule , which passes information to the receptor (and the receptor sends it to the cell) O default repression - translated "default repression", if both signaling molecules are not, the pathway is inactivated O common during development and postnatally in the immune system - effect of concentration gradient

Answer 166

- 7 signaling paths → Wnt, TGF, Hedgehog, receptor tyrosine kinases, nuclear receptors, Jak / STAT, Notch (lateral inhibition)

Answer 167

- specific cells thus prevent neighboring cells from differentiating into the same cell type O cells carry a receptor called notch ( English notch) -> signal can be bound there molecule § signaling molecules interacting with the notch are firmly anchored in the plasma membrane of cells => need for close contact ( viz. picture) - this signaling is used eg in brain -> neurons ( instead of other neurons, glial cells are formed), or also to store stem cells even in the adult organism

Answer 168

- name hedgehog -> hedgehog mutant larvae had thick hair and resembled a hedgehog (hedgehog) - these include signal molecules Sonic ( Shh, seriously), , Indian and Desert hedgehog - they move quickly and over long distances - cholesterol binds to the signaling molecule -> the complex binds to the Patched receptor -> inactivation of SMO (regulatory protein, SMO is an abbreviation for Smoothened) - SMO normally activates the expression of various genes O Shh acts as an inhibitor of differentiation - hedgehogs are morphogens involved in CNS development, neuronal migration, limb development, digestive system... - Shh mediates inductive signals between notochordem ( dorsal string, important in development, it can be imagined as a primitive spinal cord, more in lecture 5.4) and neuroectoderm ( basis of the nervous system) - holoprosencephaly - Shh is inhibited sneezing white, which leads to inactivation of signaling in the CNS, malformation of the nervous system, confusion during head formation and distribution of head cavities (including one central eye - cyclopia)

Answer 169

- Wnt proteins (wingless) = morphogens that regulate intercellular interactions during embryogenesis - participates in the determination of planar polarization and CNS development (as an antagonist and inhibitor of Shh) - is involved in intracellular signaling after Wnt binding to the membrane receptor beta catenin, which is otherwise part of the attachment of actin to intercellular junctions - Wnt and Shh are produced along the spinal cord on opposite sides, their gradient ( on the one hand a large concentration of Wnt, on the other Shh) tells neurons in what type ( motor, sensitive) to differentiate

Answer 170

- some signaling cells can get through the cell membrane directly into the cytoplasm (steroid hormones, vit A, etc.) - Vitamin A can bind to CRABP (cellular retinol-binding protein, transcription factor), which is a big problem - although vitamin A is important for the proper segmentation (breakdown, expression of the right Hox genes) of the embryo. it is also a strong teratogen

Answer 171

- TGF-β - transforming growth factors, the whole family of proteins O nodal (change from one cell type to another), lefty, BMP (bone morphogenetic proteins, induce bone growth) - FGF, VEGF, EGF, etc. - chordin, noggin, activin - surface receptors - receptor kinases (tyrosine, serine-threonine)

Answer 172

- the basic structure of the body is determined by selector, or switch genes - in lower organisms (drosophila) signals (transcription factors) are already present in the oocyte and are referred to as maternal effect genes O determine the anteroposterior (head-tail), ventrodorsal (abdomen-back) and right-left axis in drosophila O the products of these genes are growth and / or transcription factors and morphogens that can diffuse and form concentration gradients

Answer 173

- expressed only in the embryo and participate in its segmentation O the products are transcription factors or other gene regulators O in humans, they control brain segmentation (individual segments are called rhombomers) and condition the formation of pharyngeal ones arches (base of pharynx and surroundings) and somites ( "Primitive segment", lies along the notochords, they form the vertebrae, ribs, sternum, skeletal muscles, cartilage, ligaments and skin on the back)

Answer 174

- transcription factors, contain the so-called homeobox, which binds to specific regions of DNA and activates downstream genes O participates in the specific segmentation of originally identical segments O activate a number of other genes - eg genes for signal proteins or adhesion molecules (integrins) O transcription factors that contain a homeobox include, but are not limited to: § hox genes - in groups (this hox means homeobox) § craniocaudal segmentation - genes are activated and expressed in a certain way order § pax genes - development of the CNS, senses and epithelial cells § sox genes § and others - e.g. Lim

Answer 175

- first the axes, then the segmentation and then the foundations of the chest, limbs and CNS - the site of sperm entry determines the orientation of the embryo

Answer 176

- craniocaudal ( up down) -cranial ( up to the head) - caudal ( down to the feet) - ventrodorsal ( abdomen-back) -ventral ( forward, to the abdominal wall) dorsal ( back to back) - right-left axis - self explanatory

Answer 177

- before and during gastrulation (complex developmental stage, immediately after the blastocyst) - instead of entering the sperm, it decides how the zygote will divide, it determines the axis of the first division - the yolk content is then crucial for the formation of the embryonic and vegetative poles

Answer 178

- based on the formation of an oropharyngeal and cloacal membrane -> followed by the formation of a primitive band and a primitive (Hensen) node O the primitive node has the so-called nodal lashes -> they oscillate only in one direction and thus increase on one side (left) the concentration of morphogens, which determines the right-left axis - The Hensen node and the primitive strip give the cells specific information about their future location and function -> there is a so-called positional determination of cells - in this moment O the primitive stripe and the Hensen knot produce FGF8 O Nodal and lefty-2 morphogens are expressed on the left in the lateral disc, where they regulate genes to establish left-handedness

Answer 179

- precise spatial and temporal rules apply to embryo segmentation - the formation of new pairs of somites is controlled (based on the so - called. molecular clock - some genes for morphogens are periodically expressed and inactivated) - primitive node cells cyclically produce FGF and Wnt; mesenchymal cells cyclically express Notch O if a cell expresses a notch and at the same time acquires an FGF signal, it will multiply but cannot differentiate - in the next stage, the cells receive the Wnt signal, stop expressing Notch and change to an epithelial structure O Wnt is involved in the expression of adhesive molecules and planar tissue differentiation O retinoic acid and BMP or another member of the TGF family contribute to differentiation O retinoic acid and Wnt cooperate with each other and can activate pathways leading to cell differentiation - repeated periodic expression of genes allows the formation of segments (1 segment / 1 cycle)

Answer 180

- somity = primitive segments along the dorsal string ( in humans there are about 42-44 pairs of somites) - due to the planar polarization of the cells, the segment is polarized - divided into proximal and distal part O gradient of morphogens from notochord and surface ectoderm leads to division of segments into paraaxial and lateral part and subsequent differentiation of the somite into sclerotome and dermatomyotoma - further formed dermatome + myotome, from mesenchyme, base of binders § sclerotoma - the ventromedial part of each somite from which it is formed vertebrae ( the cranial part of one somite joins the caudal part of the neighboring => vertebra around the nerve fiber) * Wnt and BMP - myoblast differentiation * Shh and noggin - differentiation of sclerotomes

Answer 181

- limb segmentation works on the same principle as somite formation - ZPA - zone of polarizing activity - produces Shh and retinoic acid, mesenchymal origin O Shh controls the antero-posterior arrangement, i.e. the number of bones in segments - AER - apical ectoderm bar - produces FGF and BMP4 O FGF controls the proximo-distal axis, i.e. growth and segmentation in length - in turn, gradients are created, which express specific Hox genes and specifically differentiate the given segments (palm, forearm, arm) - apoptosis is used in finger formation - the cells stop receiving the surviving factory and die -> interdigital slits

Answer 182

- CNS development is controlled by Shh from notochord and base plate and Wnt + BMP from surface ectoderm and ceiling plate ( parts of the neural tube lying in the midline dorsally are referred to as the ceiling plate and parts lying ventrally as the base plate) - in turn, a gradient of signaling molecules induces differentiation - a higher level of BMP induces the formation of motoneurons - lateral inhibition and differentiation of neurons and glial cells

Answer 183

- infertility / sterility of the couple - inability to conceive a child during one to two years of regular unprotected sex - female infertility - inability to deliver and give birth to a viable child while retaining the ability to conceive O primary infertility - a woman is unable to conceive O secondary infertility - a woman has given birth to a healthy child once, but now she is failing - many pregnancies end even earlier than can be proven by conventional methods - 50% of all zygotes are aborted, 30% of abortions can be caused by chromosome abnormalities (60% in early abortions) - infertile is one that does not form at least one sperm - barren is one that does not produce a single egg capable of fertilization or is unable to bear fruit - Infertility affects 15-20% of couples O 33% male fertility disorder O 25% female fertility disorder O 20% fertility disorder both in pairs O 15% unknown cause

Answer 184

- examination of urine, immunological, hormonal levels, genetic examination, psychological, testis / epididymis biopsy - spermiogram - obtaining information on volume, viscosity, pH, sperm morphology, quantitative evaluation of motility, trajectory, velocity and concentration of sperm in sperm - fertile man = a man who has at least 40% progressive sperm - classification of sperm motility O type a - fast and progressively moving O type b - moving slowly and progressively O type c - mobile but non-progressive O type d - stationary -classification of sperm concentration in sperm O normospermia ( normal value) - 20mil / ml or more O oligozoospermia - below 20mil / ml O asthenozoospermia - less than 50% a + b or less than 25% a of sperm motility type O teratozoospermia - less than 30% of morphologically normal sperm O azoospermia - the absence of sperm in the semen O aspermia - absence of ejaculate O oligoasthenospermia - small amounts of sperm that are not mobile and health change recommendations O factors that can lead to decline in healthy sperms include: lifestyle changes, less sports, toxic substances - normal sperm - light gray, slightly alkaline, slightly viscous

Answer 185

- genetic causes, quantitative or qualitative disorder of spermatogenesis (in 50% of sterile men), autoimmunity to own sperm, blockage of vas deferens, coital problems, vasectomy, varicocele (dilation of veins in the scrotum, blocks sperm pathways), chlamydial or gonorrhea infections - the most common are genetic causes O aneuploidy - trisomy X / Y / 21/18/8 found in 70% of the sperm of sterile men O chromosome aberrations - inversion, ring, deletion Y, O reciprocal Y translocations with an autosome - demonstrated a higher incidence of abortions in partners of men with translocations - Cystic fibrosis - the vast majority of men with CF (95%) are infertile O The mucus typical of cystic fibrosis clogs the fallopian tubes in addition to the lungs

Answer 186

- As for sperm, an important area on Y are the AZF (AZospermia Factor) and / b / c genes on the long arm O deletions or microdeletions in these genes are found in 4% of steriles men and 16% of men with azoospermia - AZFa mutation (DBY) - absence of germ cells - AZFb mutation (RBM) - stopping spermatogenesis - AZFc mutation (DAZ) - significant fluctuations in sperm count and quality

Answer 187

- Klinefelter ( XXY) - XYY syndrome - As ever, it may or may not be sterile - Female pseudohermaphroditism ( 46, XX) - translocation of SRY to another chromosome O he has ovaries and the outer male genitalia - Androgen receptor mutations O complete - Testicular feminization syndrome § 40% of men with oligo and azoospermia § normal external female genitalia, uterus and fallopian tubes missing, testicles atrophied O incomplete - androgen resistance § XR, hypospadias (cleft urethra), cryptorchidism (testicles do not descend), micropenis - Carthagener's syndrome - AR, rare, syndrome of immobile cilia caused by dynein disorder, affected organs with mucociliary transport (bronchi), immobile sperm - Sertoli cell only syndrome (SCO) - karyotype normal 46, XY, sperm germ cells missing in testes, azoospermia O associated with germinal aplasia ( the germ layer in the embryo from which the germ cells emerge is missing) O various causes - testicular damage (intrauterine or exogenous), genetic defects

Answer 188

- lifestyle change - surgical treatment of varicocele - treatment of endocrine or immunological causes

Answer 189

- examination of fallopian tube patency, hormonal, immunological, genetic and psychological - during ovulation, progesterone, basal temperature, endometrial sample, and ultrasound are measured - genetic examination - karyotype, FISH (fluorescence in situ hybridization)

Answer 190

- genetic causes, clogged or damaged fallopian tubes , hormonal imbalance, endometriosis (presence of uterine mucosa in neighboring reproductive tissues), cervical mucus too thick , immunological sperm rejection, problems with egg nidation, premature menopause - chromosomal aberrations - aneuploidy, polyploidy, inversion, reciprocal translocations, marker chromosomes, microdeletion - Thrombophilic mutations ( increase blood clotting) O Leiden mutation for hemocoagulation factor V - AD, common (5% of the European population) § heterozygotes have a 5-10 times higher risk of venous thrombosis, homozygous 80-100x § point mutation at 1q23 § causes implantation disorders, miscarriages and premature births O Mutations in the prothrombin II gene - increased protrobin level, frequency of heterozygotes 2-3% § 3x higher risk of thrombosis O Methylenetetrahydrofolate reductase (MTHFR) gene mutation § mutation at 1p36.3, AR character § causing disorders of embryo implantation, spontaneous abortions and premature births, congenital defects of the neutral tube and coagulation disorders O prevention of all is the administration of folic acid

Answer 191

- Turner syndrome ( 45, X0 or 46, XX with deletion Xp) O 50% are mosaic forms, most are sterile - XXX syndrome - the cause is nondisjunction in M1 - Polycystic ovary syndrome - hormonal imbalance, multifactorial disorder O formation of cysts in the ovaries, infertility, oabsence of menstruation, significant hair, obesity O the cause is probably elevated androgen levels -Disorder of gonadal development O autosomal and X-linked genes, hormonal imbalances O gonadal dysgenesis or hypogonadotropic hypogonadism (delayed puberty) O Mutation of the NR0B1 gene to Xp21 - encodes DAX1 (dosage-sensitive sex reversal) § DAX1 protein nuclear receptor that acts against the SRY product O Kallman's olfactogenital syndrome - reduced function of sex hormone-producing glands § GnRH - a gonadotropin-releasing hormone is missing § no menstruation, no secondary sexual characteristics, hypogonadotropic hypogonadism

Answer 192

- sperm viability test - 6-24 hours after unprotected sexual intercourse, a mucus sample is taken from the cervix - the norm is 6 or more healthy sperm

Answer 193

- pharmacological treatment of ovulation disorders - surgical treatment of the fallopian tubes - endometriosis is treated with both

Answer 194

- all methods in which eggs or sperm are handled - methods of obtaining sperm in the case of azoospermia O TESA / TESE - extraction from testicular biopsies O MESA / MESE - extraction from epididymis by biopsy - prior to IUI, IVF and ICSI, hormonal stimulation is required for egg maturation

Answer 195

- induction of ovulation, acquisition, and washing of sperm by the spouse or donor, and transfer of sperm to the uterus by means of a catheter - indication - women with hormonal disorders, men with inability to ejaculate into the vagina

Answer 196

- the most used method - pharmacological stimulation and collection of several oocytes, cultivation in laboratory conditions with sperm and subsequent transfer the most suitable embryo (day 2 - 3) into the patient's uterus O cultivation takes place in petri dishes at 37.5 ° C and 5% CO 2 - indication - fallopian tube damage, endometriosis, sperm problems, unknown cause of sterility

Answer 197

- pharmacological stimulation, micromanipulatory fertilization by the partner's sperm and embryo transfer to the uterus - indication - sperm defects, oligoasthenospermia, azoospermia, failed IVF

Answer 198

- only sperm with the ability to bind to an egg are used for fertilization - sperm are selected with hyaluronan gel (sperm that stick together are selected for fertilization) - indication - sperm defects, oligoasthenospermia, azoospermia, failed IVF

Answer 199

- disruption of the pellucid zone of the embryo by micromanipulation technique (chemically, mechanically, laser) under a microscope, which contributes to the increased likelihood of embryo nidation in the uterine lining - indication - in case of unsuccessful pregnancy, in vitro fertilization or in women over 35 years of age

Answer 200

- fertilization in the fallopian tube with the need for laparoscopy

Answer 201

- immature oocytes are laparoscopically introduced into the fallopian tubes, later mature and the IUI comes next

Answer 202

- in vitro fertilization, early embryos (18 hours) transferred - indication - couples with immunological and suprological cause of sterility

Answer 203

- insemination with purified sperm into the mouth of the tube

Answer 204

- examination of the embryo before its implantation in the uterus - genetic PCR and / or cytogenetic FISH testing is performed - the risks of miscarriages are reduced, the percentage of births of an unaffected child increases and the success of assisted reproduction methods increases - indication - repeated abortions after spontaneous pregnancy, repeated unsuccessful artificial insemination, termination of previous pregnancy due to serious genetic disorder, birth of a child with a genetic defect, chromosome aberration of one parent, suspicion of monogenic / polygenic disease due to family occurrence or parental heterogeneity

Answer 205

- not much done, genetic (PCR) or cytogenetic (FISH)

Answer 206

- benefits - more time, without the risk of mosaicism - disadvantages - little DNA, analysis of the mother's genome only, risk of crossing-over, which leads to false positive results

Answer 207

- good and time-used method of preimplantation diagnostics - 1 or 2 blastomeres are collected two or three days after IVF from a 6-10 cell embryo - disadvantages - little DNA, amplification of information of only one allele - advantages - 2 blastomeres for mosaic exclusion, analysis of father and mother genome - in sterile couples an increased number of embryos with aneuploidies, mosaics or chaotic karyotype is found

Answer 208

- collection of 3-4 cells on day 5 after IVF - advantages - analysis of father's and mother's genome, analysis of multiple trophoblast cells - disadvantages - little time for examination - vitrification ( rapid freezing of the embryo at -196 ° C) gives time until the next cycle on Microarrays (lecture 4.21.4) examination of all chromosomes

Answer 209

- PCR - gene mutations in AD or AR diseases, mutations in male infertility - FISH - gender identification in X-linked inherited diseases, parental translocations, pericentric inversions

Answer 210

- Familial adenomatous polyposis of the large intestine - AD - Alpha-1-trypsin deficiency - AR - Cystic fibrosis - Duchenne muscular dystrophy - XR - Fragile X syndrome - Hemophilia A and B - XR - Huntington's disease - AD - Marfan's syndrome - AD - Sickle cell disease - AR - Tay-Sachs disease - AR - Thalassemia - AR - Spinal muscular atrophy - AD, AR - Myotonic dystrophy - AD

Answer 211

= primary undifferentiated cell, from which only by further division and differentiation (due to the action of growth and differentiation factors) mature cells fulfilling a certain function are formed O is able to create its own identical copy (clone) and differentiation - morphology: spherical cells, heterochromatic nucleus, few cytoplasms

Answer 212

- totipotent stem cell O cells formed the first division of the egg O they can give rise to any cell/tissue (including trophoblast) → one totipotent cell can give rise to a whole new individual - pluripotent stem cell O they can give rise to any tissue of ectoderm, endoderm and mesoderm O they cannot give rise to a trophoblast - multipotent stem cell O they can produce only cells related to the cell type § hematopoietic cells § skin stem cells § neural stem cells - olipotent stem cell - unipotent stem cell O they can produce only one cell type however, they have the ability to fully recover themselves

Answer 213

o = embryonic cells in the stage of morula or blastocyst (up to about 150 cells) O ESCs require specific signals to initiate proper differentiation O When directly inserted into another body, the ESC splits uncontrollably into many different cell types, which can cause teratoma O ESC research - ethical aspects O the first human ESCs were isolated in 1998, the mouse ESCs as early as 1991

Answer 214

O somatic stem cells O their primary function is to maintain and repair the tissues in which they are found, in the organisms of young individuals i older O pluripotent adult stem cells are generally rare and form very small colonies -> can be found in umbilical cord blood, or also in other tissues such as bone marrow O Transient amplifying cells O hematopoietic stem cells, stem cells in the epithelium intestines, in the epithelium of the epidermis, in the mammary gland...

Answer 215

O they are multipotent stem cells with ability self-renewal and at the same time differentiation into osteoblasts, chondroblasts, myoblasts, fibroblasts, adipocytes and stromal cells O are characterized by the expression of surface markers: CD29, CD44, CD73, CD90, CD105 and CD106 O we do not find in them: CD31, CD33, CD34 or CD45, which are typical of hematopoietic stem cells

Answer 216

O these cells are most similar in their properties to embryonic stem cells and have a wide differentiation potential O it is not possible to find these cells in a developing or adult organism -> prepared by artificially targeted modification already differentiated cells of the body - most often fibroblasts o ( a number of other cells can be used as the initial cell type, for example hepatocytes, various blood or neuronal cells cells)

Answer 217

- Stem cell niche (niche) = a special microenvironment in which stem cells reside - provides nutrition, protects against differentiation and apoptotic signals from the environment, prevents excessive stimulation of cell proliferation, which could result in tumor growth

Answer 218

1. permanent, incapable of regeneration (cardiomyocytes, neurons, lens cells) 2. stable, Signs of mitotic activity are shown by less than 1.5% of cells, with limited regenerative capacity, their regeneration is accelerated by damage (liver, kidneys, endothelium, fibroblasts, smooth muscle) O glandular epithelium - the liver, the lining of the tubules of the kidney, regenerate for a long time and only under certain conditions 3. labile, constantly regenerating - more than 1.5% of cells show mitotic activity (hematopoietic bone marrow, superficial epithelium - skin, urogenital tract, cornea and intestinal mucosa, etc.), their constant renewal is essential for life O regeneration of covering epithelia - reepithelialization in the case of a deeper defect, granulation tissue is first formed O the exception is the intestine: even a deeper defect heals only by reepithelialization O they do not regenerate the adnexa, so the scar is dry, without hair O the epithelium of the oral cavity regenerates rapidly

Answer 219

- science that studies the causes, mechanisms and patterns of abnormal development - causes of birth defects - we do not know (50%), multifactorial (25%), environmental effects (10%), mutated genes (8%) and chromosomal abnormalities

Answer 220

- teratogens (exogenous influences that can cause developmental defects) O drugs - see below O chemicals - polychlorinated biphenyls, methylmercury, alcohol, thalidomide O infection - rubella (rubella), herpes viruses, toxoplasma, syphilis, zika virus O ionizing radiation - X-ray O maternal factors - diabetes, fever (above 39 ° C for more than 24 hours dangerous), phenylketonuria, hyper / hypothyroidism

Answer 221

- congenital malformations - 2-3% newborns -> embryos are affected much more (about 15%), but these embryos are more likely to have an abortion O during life, malformations are found in other children - 6% under 2 years, 8% under 5 years and another 2% later - abnormality - 14% of newborns - the most common malformations O men - hypospadias (cleft of the urethra on the underside of the penis) O women - hip dysplasia O narrowing of the aorta is slightly less common

Answer 222

- definition of teratogen - a factor that is present in the environment in an amount that increases the incidence of embryotoxicity above the baseline frequency in the unexposed population O technically, each substance can be teratogenic (in a certain amount) → however, most of these substances are harmless in small quantities - teratogenesis is a process with a threshold effect - analogue of multifactorial inheritance, the effect of teratogen needs to get over the dose threshold, it starts to work only from a certain amount - teratogenicity is a manifestation of developmental toxicity representing a special case of embryo / foetotoxicity that induces or causes an increase in the frequency of structural disorders in the offspring - critical period of development - individual for each teratogen and organ system O Teratogens act mainly during cell division, so tissues are most sensitive during the beginning of their development O in general, the most sensitive period is weeks 3-8, because the limbs and most systems are established (organogenesis) - during sensitive periods ( typically critical) the embryo is still susceptible to teratogen, but not so much, it needs a larger dose of teratogen and there will be fewer abnormalities or functional defects - the genotype of the embryo and mother also plays a big role here - they affect the teratogenic threshold and the duration of critical and sensitive periods

Answer 223

- generally anything that can affect signaling, fetal cell proliferation or bleeding - Thalidomide - Cytostatics - Anticoagulants - Warfarin and other Coumarin derivatives - Anticonvulsants - Retinoids and vitamin A - Alcohol - Androgens - Diethistylbestrol - Folic acid antagonists - Lithium - Ribavirin - Mycophenolate mophetil - ACE inhibitors - Nonsteroidal antiphlogistics

Answer 224

- diabetes - epilepsy - phenylketonuria - autoimmune diseases - asthma - tumors - chickenpox - dangerous especially between the 12th and 20th week of pregnancy

Answer 225

- tissue with cell renewal - cells wear out due to exposure and functional load and are constantly replaced by new ones (epidermal cells, intestinal mucosa, blood cells) - tissue without cell renewal - permanent cells, in case of loss they cannot be replaced (neurons, eye lens cells, heart muscle cells, sensory cells for light and sound) - tissue regeneration O physiological recovery - renewal of worn cells (skin, intestinal mucosa, hematopoiesis) O reparation - replacement of damaged or lost cells (tissues and whole organs) § it is further divided into reparative regeneration and wound healing

Answer 226

- two mechanisms of physiological cell renewal, both through proliferation - fully differentiated cells also proliferate O proliferation of differentiated cells ( hepatocytes, endothelial cells - vessels) O recovery from undifferentiated cells progenitor cells ( epidermis, hematopoiesis)

Answer 227

O are undifferentiated O have the ability to proliferate throughout the life of the organism O after mitotic division, one daughter cell differentiates and one remains a stem cell § this division is called asymmetric § the daughter cell that differentiates has been mitotically divided beforehand, and hundreds of cells can be formed from one daughter cell

Answer 228

O embryonic stem cells - produce all embryonic cells O adult stem cells - replace only cells of finished organs

Answer 229

O totipotent - able to differentiate into any cell of the organism and create a completely new individual § zygote + cells a few more dividing zygotes O pluripotent - descendants of totipotent cells, can produce any germ leaf cells § multipotent - partially differentiated pluripotent cells, have only limited possibilities of differentiation § hematopoietic stem cells, intestinal mucosa stem cells O unipotent - they can only produce one type of cell, but they can regenerate themselves § epidermal stem cells - they are in charge of regulating physiological cell renewal Cytokines - HGF (hepatocyte growth factor), interleukins, and erythropoietin

Answer 230

- keratinocytes - they synthesize keratin, are on the surface, and are stuck in the middle of apoptosis - unipotent stem cells - their daughter cells differentiate into keratinocytes O the basal layer ripples variously, the stem cells are at the tips of these ripples

Answer 231

- stem cells are located in the lower part of Lieberkühn's crypts, differentiation upwards - the intestinal mucosa contains two types of cells (absorption and secretion), so we need a stem cell that can differentiate into two types of cells - pluripotent - Wnt (induces proliferation) and Notch signaling (secretory cells inhibit differentiation of surrounding cells to other secretory ones)

Answer 232

- hematopoietic stem cell - pluripotent - main proliferation takes place along two lines - lymphoid (B and T lymphocytes) and myeloid (erythrocytes, monocytes, platelets)

Answer 233

- via cytokines - eg M-CSF regulates monocyte production

Answer 234

- two mechanisms of repair - repair regeneration and wound healing

Answer 235

- restoration of the original function and morphology of the damaged tissue - the ability to regenerate varies between organisms, vertebrates (except tailed amphibians) have only limited ability to regenerate (but eg liver or bone tissue can still regenerate) - the process takes place by so-called dedifferentiation and redifferentiation O the differentiated cell "returns" to the undifferentiated cell, begins divide and then re-differentiate into the same cell type - embryonic stem cells are used therapeutically to regenerate damaged organs

Answer 236

- the destroyed tissue is replaced by a connective tissue - a scar - fibroblast scar - a signaling molecule for fibroblast proliferation is PDGF (platelet derived growth factor), which is produced by almost every cell around the wound - thanks to warm-bloodedness, regeneration is very energy and time consuming, evolutionarily it was better to just seal the wound with a scar

Answer 237

- organ damage compensation mechanisms - compensatory hyperplasia - damage to a part of an internal organ leads to the replacement of the required number of cells by increased proliferative activity of cells of an undamaged part of the same organ - eg liver - compensatory hypertrophy - when one of the two pairs is damaged, the proliferative activity of the cells of the other (undamaged) organ - eg the kidneys - occurs

Answer 238

- originating from photosynthesis - first O2 Oxygen appeared 2 billion years ago as a result of cyanobacterial photosynthesis - enabled aerobic metabolism - is essential in maintaining two basic balances in the body O acid - base forward proton § base + H + <-> acid O oxidation-reduction balance - handover electron § oxidized form + e- <-> reduced form

Answer 239

- in the body, oxygen is gradually reduced to water in the presence of oxidoreductases, electrons and hydrogens O O 2 + 4e- + 4 H + → 2 H 2 O O intermediates are reactive oxygen species (ROS) 1. superoxide O O 2 + e--> O 2- * O in the valence sphere the unpaired electron is -> very reactive 2. hydrogen peroxide O O 2- * + e- + 2 H + -> H 2 O 2 O it is produced in peroxisomes by oxidation of alcohol to acetaldehyde O is more stable than superoxide (so it's not that dangerous) 3. hydroxyl radical O H 2 O 2 + e- -> OH- + OH * 4. water O OH * + e- -> OH- O 2 OH- + 2 H + -> 2 H 2 O - During this process, ROS are bound to oxidoreductases where they are harmless, but sometimes they enter the cytosol, where they oxidize nucleic acids, proteins...

Answer 240

- respiratory chain (aerobic phosphorylation) O 1 - 4% of oxygen is incompletely reduced and superoxide is formed O complex I - NADH-ubiquinone reductase O complex III - ubiquinol-cytochrome C reductase - cytochrome P-450 and monooxidases in liver ER O cytochrome P-450 - biotransformation of xenobiotics and oxidation of ethanol (yaaaay) O monooxygenase - synthesis of cholesterol and bile acids - specialized cells - leukocytes, macrophages O NADPH oxidase in the cytoplasmic membrane - bactericidal protective system, help with respiratory inflammation (enrage of white blood cells, after phagocytosis of pathogens they consume a lot of oxygen to produce toxic substances, thus destroying pathogens inside the cytoplasm) neutrophils and macrophages O myeloperoxidase - production of HClO, which decomposes into hydroxyl radical and chloride anion and serves for destruction bacteria - oxidation of hemoglobin and mathemoglobin O in the oxidation of iron ((Fe 2+ -> Fe 3+ + e-) an electron is released, which is transferred to oxygen and superoxide is formed

Answer 241

- superoxide dismutation O 2 O2- * + 2 H + -> O 2 + H 2 O 2 O spontaneous in the presence of the enzyme superoxide dismutase - direct reduction of O2 by oxidases O monoamine oxidase, glutathione oxidase, xanthine oxidase - peroxisomes O consume O 2 and form peroxide by oxidation of ethanol, phenols and formaldehyde O ω-oxidation of long (> C18) and branched fatty acids

Answer 242

- quinone antibiotics - pyridine herbicides - low molecular weight Fe complexes with phosphates or nucleotides

Answer 243

Nitric oxide NO - significant second messenger - antimicrobial effects - macrophages - nitric oxide synthase - NOS O NOS I - cerebral (brain) O NOS II - macrophage O NOS III - endothelial Peroxynitrite - NO- + O 2 * - -> OONO- - significant oxidizing agent - oxidizes amino acids in proteins - antimicrobial effects - macrophages

Answer 244

- reduction of excessive ROS and RNS formation O regulation of enzyme activity O uptake of transit elements (ions) from reactive sites - capture and removal of generated radicals O catchers, traps, fire extinguishers O enzymes and other radical scavengers together form more stable products - general repair mechanisms of damaged macromolecules O phospholipases O DNA repair enzymes O proteolysis of oxidatively damaged proteins

Answer 245

- the first step is the conversion of the dangerous superoxide to milder hydrogen peroxide O superoxide dismutase enzyme - hydrogen peroxide proceeds in one of three reactions O fenton reaction - peroxide together with Fe 2+ forms Fe 3+ and hydroxyl radical O in the presence of catalase for water and oxygen O in the presence of glutathione peroxidase to water

Answer 246

- superoxide dismutation is spontaneous, SOD only accelerates it (about 10,000x) - present in most aerobic cells and extracellular fluid - several isoenzymes with different metallic cofactors O mitochondrial SOD2 = MnSOD § most important (inactivation in mice leads to their death soon after birth) § it is also in prokaryotes and in the mitochondrial matrix O cytoplasmic SOD1 = CuZnSOD § in the cytosol and intermembrane space of mitochondria § its deactivation reduces life expectancy - degenerative diseases and cancers develop O extracellular SOD3 = ECSOD § its deactivation has only a minimal effect

Answer 247

- removes oxidation products of cell membranes - coenzyme glutathione ( tripeptite GluCysGly, electron source) O glutathione has an abbreviation GSH - GSSG is glutathione disulfate - removal of intracellular hydroperoxides (reduce peroxide) - they are selenoproteins - they have selenocysteine in the active center - 2 GSH + ROOH = GSSG + H 2 O + ROH - two types O cytosolic GSH - glutathione peroxidase (cGPx) § decomposes fatty acid hydroperoxides upon release from lipids O phospholipid hydroperoxide-GSH-peroxidase (PHGPx) § reduces phospholipid hydroperoxides directly in the plasma membrane without releasing fatty acids from phospholipids

Answer 248

- dismutates hydrogen peroxide - 2 H 2 O 2 <-> 2 H 2 O + O 2 - the cofactor is heme - inactivation H 2 O 2 in peroxisomes and hepatocyte mitochondria, erythrocyte cytoplasm

Answer 249

- they are proteins that bind free Fe and Cu ( so-called transit metals) , thereby inactivating them - transferrin - binds Fe 3+ in plasma - ferritin - intracellular, has ferroxidase activity (oxidizes Fe 2+ and Fe 3+) and also functions as a reservoir of Fe in the cell - haptoglobin - scavenges extracellular hemoglobin - ceruloplasmin- binds Cu in plasma, oxidizes Fe binds Cu in plasma, oxidizes Fe 2+ -> Fe 3+ - albumins - binds Cu through its SH groups - metallothionein - binds metal ions in the nucleus, they contain cysteine residues

Answer 250

- soluble in water - dissolved in the cytoplasm and blood plasma O ascorbic acid (vit C), glutathione, uric acid, lipoic acid - fat soluble - part of phospholipid bilayers O carotenoids and vit A, α-tocopherol (vit E), ubiquinol (coenzyme Q)

Answer 251

- monosaccharide derivative occurring in animals and plants (but not synthesized in humans) - important for collagen synthesis, formation of hydroxyproline - reduces radicals (O 2- *, HOO *, HO *, ROO *, NO 2) by splitting hydrogen and donating it to the radical, thereby neutralizing it - by oxidation Vit C itself converts to its radical form (hydroascorbate), but it is a large molecule, slow relatively stabilized and quite harmless - hydroascorbate regenerates by reduction of NADH or dismutates to ascorbate and dehydroascorbate - in combination with Fe it has a prooxidant effect O reduces Fe 3+ and Fe 2+ and Cu 2+ O helps absorb Fe in the intestines

Answer 252

- Vitamin E is the collective name of 8 natural substances - isomers - of which the most important is α-tocopherol - α-tocopherol O reduces the alkyl peroxyl radicals of LOO * lipids to hydroperoxides, which are then reduced glutathione peroxidase O oxidation converts to a low-reactive tocopheryl radical and regenerates back thanks to ascorbate (vit A and E work together) O occurs in cereals, liver and eggs

Answer 253

- part of the respiratory chain in mitochondria - antioxidant in mitochondria and membranes - partially synthesized, partially ingested by food - with age, its content in mitochondria decreases

Answer 254

- chemically isoprenoids - they remove carbon-centered radicals and LOO * in lipids - the resulting kerotene radical is very stable, because the extra electron jumps all over the structure

Answer 255

- tripeptide - g-glutamylcysteinylglycine - is synthesized in the body - the most important intracellular redox buffer - GSH non-enzymatically removes ROS ( HO *, RO *, ROO *) - maintains in reduced form SH groups of proteins, cysteines, CoA and regenerates ascorbate - the enzyme glutathione reductase catalyzes the regeneration of glutathione by the cofactor NADPH

Answer 256

- end product of purine degradation in humans and primates - the most important antioxidant of plasma - captures RO *, HClO and binds Fe and Cu - too much uric acid = hyperuricemia (dangerous, gout)

Answer 257

- supports metabolism - is a cofactor of pyruvate dehydrogenase and α-ketoglutarate dehydrogenase complex

Answer 258

- oxidative stress - disturbance of the balance between the formation and removal of ROS and RNS O either excessive production of radicals or insufficient protection - causes of overproduction of ROS and RNS O tissue reoxygenation after ischemia O after ingestion of redox-active xenobiotics O by releasing Fe and Cu from bonds from storage proteins O excessive NO production and excess SOD capacity § NO + O2- * -> ONOO- * - peroxynitrite (strong oxidant)

Answer 259

- Fenton reaction - Fe 2+ + H 2 O 2 -> Fe 3+ + HO * + OH- HO * + OH- - the catalytic ability of Fe in the active centers of enzymes - substrate selected for the benefit of the organism - Fe reacts in this way even with non-specific binding to proteins, lipids, NK - after escape from transferrin and ferritin = damage to molecules - the human body contains about 4 grams of Fe - of which 70% is in hemoglobin and 10% in myoglobin

Answer 260

- the most prone to oxidation are double bonds in MK (ie unsaturated MK) O in vitro - oil rancidity - autooxidative radical reaction O in vivo - lipid peroxidation - polyenoic fatty acids - non-enzymatic peroxidation O caused by non-specific pathological factors O MK is split into hydrocarbons (ethane, pentane, aldehydes), which reduces the fluidity of membranes - enzyme peroxidation O hydroperoxidase enzymes - produce biologically active prostaglandins (paracrine signaling molecules)

Answer 261

- reaction with HO * - hydrogen is removed from deoxyribose and chain interrupted or by base addition (to form hydroxy or oxy derivatives)

Answer 262

- oxidation of amino acid residues O methionine -> methionine oxide O cysteine -> cysteic acid O arginine -> glutamic acid aldehyde O proline -> glutamic acid - hydroxylation of aromatic amino acids (eg phenylalanine -> tyrosine) - lipoperoxidation products (hydrocarbons) bind to NH 2 a group of lysine where it accumulates - NH damage 2 groups at the Fe binding sites

Answer 263

- at high concentrations, glucose (reactive substance) binds to NH 2 groups of proteins - non-enzymatic glycation (so-called Maillard reaction) O early (hours) - labile Schiff base (aldimine) is formed O transient (days) - glycated proteins fructosamines are formed (Amari products) O advanced (weeks, months) - the chains are linked to the compound AGE (advanced glycation end product) - glycated hemoglobin O serves as a long-term return glycemic control in diabetics (2-3 months)

Answer 264

- the science of poisons - definition of poison O a poison is a substance that can cause poisoning § All substances have the properties of poison - it is the dose that makes poison out of things - the irreversibility of the effect makes the substance a poison O legislators - poisons are substances that cause poisoning in single small and repeated doses and are listed in poison lists O LD ( z angl. lethal dose, latin dosis letalis) § aconitine - LD 3 mg, reduces the ion selectivity of ion channels in the cell membrane of plant species thistle, eg thistle wolf plague § As 2 O 3 - arsenious oxide aka arsenic or puff, LD 400 mg arsenious oxide aka arsenic or puff, LD 400 mg arsenious oxide aka arsenic or puff, LD 400 mg arsenious oxide aka arsenic or puff, LD 400 mg arsenious oxide aka arsenic or puff, LD 400 mg arsenious oxide aka arsenic or puff, LD 400 mg arsenious oxide aka arsenic or puff, LD 400 mg § NaCl - 250 g § Distilled water - 15 liters, such an amount changes the osmolarity of the blood and thus bursts the erythrocytes

Answer 265

- result of the interaction between the substance and the organism, some substances are not toxic until they are metabolised - effect and its size depends on O active substance - chemical constitution § polarity of bonds - hydrophobic substances stay longer in the body (because they are stored in fat cells) § reactivity - the more functional groups (carboxyls, epoxides, amines) the more toxic the substance § spatial arrangement O exposure § dose - the amount of the substance per individual weight § Representation of the substance in the environment - given in ppm (pars per million) = mg / kg, ppb (pars per billion) = μg / kg § duration of contact - for example, when irradiating how long a person has stood in front of a radioactive substance § method of resorption - a method of penetration of a substance into the body, eg some substances are harmless if they do not get directly into the bloodstream directly O organism § species, tribe, genus § age, gender, health status § individual, inherited and acquired traits - everything, including isomerism, plays a role in the effect of the substance O thalidomide - sold under the name Contergan as a sedative in the 1950s and 1960s in pregnancy § R-enantiomer was effective in morning sickness § S-enantiomer was a teratogen, that caused severe malformations or complete absence limbs in about 12,000 children

Answer 266

- nonspecific O the result of the general physico-chemical action of the poison § anesthesia- N 2 O, diethyl ether- prevents the transfer of ions across the membrane § corrosive (sulfuric, nitric acid) or oxidizing agent - tissue degradation, cell destruction - specific O the result of a specific intervention in a certain biochemical event O chemical configuration x receptor O specific substances are toxic even in 100x lower concentrations (milligrams) O fluoroacetic acid - aconitase inhibitor, stops the Krebs cycle and the cells so they die of lack of energy, an organic plant poison, used as a pesticide

Answer 267

- acute O single administration of a higher dose O it will show up immediately or in a very short time O it usually has very serious health consequences O acute toxicity expressed as fatal dose - eg LD 50 kills 50% of the poisoned, LD 100 kills everyone - chronic O after long-term exposure to low doses O manifests itself after a long time (months, years) O symptoms of acute and chronic effects they are not usually the same - late O manifestation after a long period of latency O the effect of the chemical may no longer exist O carcinogens and mutagens - manifestations may occur several years after exposure, which could be acute

Answer 268

- local effect - acids, bases, oxidants - tissue degradation, cell lysis, burns (sulfuric acid, hydrogen chloride, hydrogen fluoride) - aldehydes, alkylating and acylating agents - react with proteins (formaldehyde) - pneumoconiosis - induce changes in the structure of the lungs by inhalation of dust (silica, asbestos)

Answer 269

- overall effect - volatile solvents - prevents ion transfer through the phospholipid bilayer - gasoline, benzene, toluene, CCl4, C2 Cl4, inhalation anesthetics - dissolution in membranes inhibits the transmission of nerve impulses and thus suppresses the activity of the nervous system

Answer 270

- interaction with the hemoglobin binding site for O2 -- CO, NO (Fe bond 2+ with CO it is 300 times stronger than with O2) - hemoglobin oxidizing agents ( Fe 2+) to methemoglobin (Fe 3+) - nitrites, chlorates, nitrobenzene, aniline - cytochrome oxidase inhibitors ( complex IV) - HCN, H 2 S (both bind to iron)

Answer 271

- heavy metal ions ( Hg 2+, Pb 2+, CD 2+, AsO 33-) and alkylating agents react with SH and NH2 groups of enzymes, thereby abolishing their tertiary structure - eg Pb 2+ blocks porphobilinogen synthetase, which is important in heme synthesis - substrate analogs - fluoroacetic acid inhibits aconitase - organophosphates and carbamates - inhibit acetylcholinesterase ( causing paralysis)

Answer 272

- induction of cytochromes P-450 of the endoplasmic reticulum in the liver - change in the rate of biotransformation, increased amount of metabolites, faster synthesis of enzymes - phenobarbitals, PCBs, PAHs, dioxins (inducers often procarcinogens)

Answer 273

- alkylate nitrogen bases of DNA, RNA and proteins - have mutagenic and carcinogenic effects - dimethyl sulfate, diazomethane, ethylene oxide, methyl iodide, dimethylnitrosamine

Answer 274

- CCl 4, O 3, halogenated hydrocarbons, benzopyrene - protein inactivation, lipoperoxidation of polyenoic fatty acids - exhalation of ethane and pentane

Answer 275

- mutagens - cause a change in genetic information O germ cell mutations - transmission of damage to the next generation O Somatic cell mutations - can cause cancer - carcinogens - create tumors benign or malignant (metastatic) not necessarily by altering the primary structure of the cell's DNA O long latency period of chemical carcinogens (10+ years) - 80-90% of carcinogens are mutagens at the same time, both effects are accompanied

Answer 276

- Chemical carcinogens covalently bind to DNA, causing errors in replication or transcription - organic carcinogens - polycyclic aromatic compounds, aromatic amines, chlorinated biphenyls, azo compounds, asbestos, epoxides, aflatoxins, nitrosamines... - inorganic carcinogens - arsenic, chromium (its hexavalent compounds), cadmium, nickel - metal and polymer implants - eg asbestos fibers O thin layers, fibers, powders (several μm) - mechanisms of action of chemical carcinogens O basic principle of carcinogenicity - the carcinogen covalently binds to a biological macromolecule O sometimes the substance is not carcinogenic, but its metabolite is - the so-called biotransformation of the primary carcinogen § procarcinogen ( maternal carcinogen) -> intermediates -> terminal carcinogen

Answer 277

- sources of pollution - smoking, internal combustion engines, grilling, chemical industry - coal tar - a raw material for the production of dyes and medicines - they are substances insoluble in water - they sublimate - Vapors are irritating to the eyes and skin, affect the kidneys and liver, reduce fertility and are teratogenic - Carcinogenicity has been demonstrated (so far) in 15 polycyclic aromatic hydrocarbons - benzopyrenes - cigarette smoke, coal combustion, exhaust gases (imperfect combustion below 600 °C) O they are caught in the lungs (lung cancer), they can also enter the body through the digestive tract or skin contact O one of the strongest carcinogens

Answer 278

Polychlorinated dibenzodioxins / dibenzofurans - PCDD / F = Dioxins - solids, slightly soluble in water, are sorbed on sludge and plankton - highly unstable - decomposition by UV, accumulates in adipose tissue, can be concentrated in the food chain - PCDD / Fs have no practical use and have not been intentionally produced, they are by-products of pesticide production and combustion O the most toxic is TcCDD (2,3,7,8-tetrachlorodibenzodioxin), it serves as a baseline (others are converted to it) - damage the liver and other organs, including specific skin disease (chloracne), they also have a teratogenic effect

Answer 279

- cooling charges in transformers and condensers, hydraulic fluids, paints - similar effects as dioxins (chloracne, liver damage, carcinogenesis, teratogenesis) - environmental pollution - leaks from transformers - concentration in the environment - soil -> water -> plankton -> fish (the most important source of PCBs)