Chapters11-16 Flashcards
Mitosis
Segregation and replication of the DNA in a Diploid cell.
A single nucleus gives rise to two nuclei that are geneticall identical to each other and to the parent nucleus. Accurate segregation of the eukaryotic cells multiple chromosomes into daughter nuclei.
Diploid Cell
diploid cell is a cell that contains two sets of chromosomes.
Chromatin
single strand of a chromosome, and it is the complex of DNA and proteins
Centromere
Is part of the chromosome that holds the two sister chromatids together.
Histones
Are proteins that are positively charged, and they help package the eukaryotic DNA. They are positively charged because of their high content of the basic amino acids lysine and arginine.
Nucleosomes
Is the basic unit of DNA packaging in Eukaryotes, consisting of a segment of DNA wound in sequence around four histone protein cores.
Centrosome
An organelle in the cytoplasm near the nucleus. It serves as the main microtubule organizing center. It usually consists of a pair of centrioles
Centrioles
A pair in each centrosome, Hollow tube formed by nine triplets of micotubules. The two tubes are right angles to each other.
How does the Centrosomes determine the plane of cell division?
During S phase the centrosome doubles to form a pair of centrosomes. G2 to M transition, two centrosomes separate from one another moving to opposite ends of the nuclear envelope. Positions of the centrosomes determine the plane at which the cell will divide.
What are microtubules and how are they formed?
Centrioles are surrounded by high concentrations of tubulin dimers these proteins then form the microtules that orchestrate chromosomal movement.
What happens in prophase in mitosis?
1) chromatin fibers become coiled into chromosomes with each chromosome having two chromatids that join at a centromere.
2) the mitotic spindle, composed of microtubules and proteins form in the cytoplasm (serves as a structure to which the chromosomes attach and act as a framework)
3) the two pair of centrioles move away from one another and it serves as a mitotic center(poles of the cell)
What is the Spindle?
Array of microtubules spreading out from both poles of a dividing cell during mitosis.
What are the two types of microtubules in the spindle?
Polar microtubules and kinetochore microtubules
What is a polar microtubule?
Acts as a frame work of the spindle, and runs from one pole to the other attaching to the centrosomes
What is a kinetochore microtubule?
Attach to the kinetochores on the chromosomes
What is a Kinetochore?
is the protein structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart
List the steps in Mitosis
Prophase, Prometaphase,Metaphase,Anaphase and telophase
What happens in Mitosis prometaphase?
The nuclear envelope breaks down and the compacted chromosomes attach to the kinetochore microtubules.
What happens in Mitosis Metaphase?
The microtubules pull the chromosomes to a equatorial position in the cell.
What happens in Anaphase in Mitosis?
The paired sister chromatids separate, and the new daughter chromosomes begin to move toward the poles. Separation occurs because on subunit of the cohesin protein holding the sister chromatids are hydrolyzed by an enzyme called protease but a specific variation of this enzyme called separase. After they separate the chromatids are called daughter chromosomes.
What happens in telophase in mitosis?
Occurs after the chromosomes have reached the poles, a nuclear envelope forms around each set of chromosomes, The chromatin decondenses.
What happens in Cytokinesis in a eukaryotic cell?
A single eukaryotic cell is divided to form two daughter cells. It begins with a pinch of the plasma membrane called a contractile ring. It is composed of microfilaments of actin and myosin, they pinch the cell in two.
Asexual reproduction.
Mitosis based, the offspring are clones, they are genetically identical to the parents.
Sexual reproduction
Consists of both mitosis and meiosis, the organism is not identical to its parents.
Haploid
It is a Gamete( is a cell that fuses with another cell during fertilization) which contains only a single set of chromosomes. N
Gamete
Mature sexual reproductive cell” the egg or the sperm.
Zygote
Two haploid gametes fuse to form a zygote in fertilization, Have two sets of chromosomes. Its chromosome number is 2n. This is basically a diploid cell.
Somatic cells
All cells of the body that are not specialized for reproduction.
Homologous pair
Two chromosomes bear corresponding, might not be identical genetic information.
Homologs
one pair of chromosomes having the same ove
What does meiosis do?
Nucleus divides twice, but DNA is replicated only once.
Reduce chromosome number from diploid to haploid
Ensure the haploid products have a complete set of chromosomes
Generate genetic diversity
What happens in Meiosis 1.
Homologus chromosomes come together to pair along their entire lengths.
The homologous chromosome pairs separate but the individual chromosomes, consisting of two sister chromatids remain intact.
What happens in Meiosis prophase 1:
The homologous chromosomes pair by adhearing along their lengths called synapsis. The chromosomes coil and compact, then these sister chromatids take on a X-shaped appearance called Chiasmata, This causes the chromatids to Crossover, which causes the transfer of genetic material. The final product is recominant chromatids.
What is Synapsis
Homologous chromosomes pair by adhearing along their lengths
Karyotype
Number shape and sizes of the chromosomes in a cell
Tetrad
When four chromatids of each pair of homologous chromosomes to form a tetrad
Chiasmata
Regions having attachments mediated by cohesins take on an X-shaped appearance
Crossing over
Chiasma reflects an exhange of genetic material between nonsister chromatids on homologous chromosomes
Recombinant
Crossing over results in recombinant, it increases genetic variation among the products of meiosis by reshuffling genetic information among the homolgous pairs.
What happens in Metaphase 1 in meiosis
Homologous pairs align at the equatorial plane
What happens in Anaphase 1 in meiosis
Centromers do not separate: sister chromatids remain together during anaphase, homologs separate.
Telophase 1
Two homologs are segregated from one another and the cell pinches in two.
Reciprocal crosses
Plants were crossed (mated with each other) in both directions like white flower with red.
Gregor Mendel who is he and what did he do?
An Austrian monk who worked on genetics of pea plants
Character
An observable physical feature, such as flower color
Trait
A particular form of a character, such as purple flowers or white flowers
Heritable trait
Is a trait that is passed from parent to offspring
True-breeding
Observed trait was the only form present for many generations, they have the same alleles
How did Mendel perform his crosses?
He removed anthers from the flowers so that it couldnt self pollinate. He then collected pollen from the other parental strain and placed it on the stigmas of flowers of the removed anthers. Plants providing and receiving the pollen were the Parental generation.
First filial generation
F1: seeds formed producing new plants this is the first generation
Second filial generation
F2: the second generation from self pollination
Hybrid
Offspring of crosses between organisms differing in one or more traits
Monohybrid cross
F1 seeds allowed to self-pollinate to produce the F2 generation
Particulate Theory
The units of inheritance retain their integrity in the presence of other units.
Haploid
Single set of heritable units
Diploid
Two copies of genes unit in an organism
Gene
A sequence of DNA that is transcribed into a functional RNA molecule.
Genome
Totality of all the genes of an organism
Alleles
Different forms of a gene Example (S and s)
Homozygous
They have two copies of the same allele (ss)(SS)
Homozygote
An individual that is homozygous for a character
Heterozygous
They have two different alleles of the gene
Phenotype
The physical appearance of an organism
Genotype
Genetic consitituion, S or s dominate or Ressesive. SS,Ss,ss
Law of Segregation
When any individual produces gametes, the two copies of a gene separate, so that each gamete receives only one copy.
Locus (loci)
A gene in a sequence of DNA that resides at a particular site on a chromosome. A specific part of a chromatid.
Test cross
Way finding out if it is Ss or SS you cross it with ss and the punnett square should tell you if its either SS or Ss
Di hybrid cross
Cross between individuals that are identical. Double heterozygotes
Mutation
Rare stable and inherited changes in the genetic material. An allele can mutate to become a different allele.
Wild type
This allele is the one that is present in most individuals in nature. Gives rise to an expected trait or phenotype.
Polymorphic
Two or more clearly different phenotypes exist in the same population
Incomplete dominance
Neither of the two allels is dominant, it is a blend of the phenotype of a heterozygote
Codominance
Two alleles at a locus produce two different phenotype that both appear in heterozygotes
Pleiotropic
When a single allele has more than one distinguishable phenotypic effect.
Epistasis
The phenotypic expression of one gene that is affected by another gene.
Heterosis( short for heterozygosis)
Hybride vigor after crossing inbrad lines
What can effect a phenotype?
genotype and environment interact to determine the phenotype of an organism. Enzymes encoded by the gene activated or inactivated based on the environment
Penetrance
is the proportion of individuals in a group with a given genotype that actually show the expected phenotype
Expressivity
The degree to which a genotype is express in an individual
Quantitative trait loci
Are refered to phenotypes that vary in degree and can be attributed to polygenic effects product of two or more geners, and their environment
What happens to a chromosome when two loci are on the sae chromosome
They might be linked
Progeny
A genetic descendant or offspring
Recombinant frequencies
The proportion of offspring of a genetic cross that have phenotypes different from the parantal phenotypes dur to crossing over between linked genes during gamete formation
Monohybrid
Ss SS
Di hybrid
SsGg SSGG
Corssing over in Loci
The more far apart they are they more likely crossing over will occur.
Nondisjunction
A pair of homologous chromosomes (in meiosis 1) or sister chromatids (in meiosis 2) fail to separate.
Aneuploid
having fewer or more chromosomes than normal,nondisjunction can cause this.
Primary sex determination
SRY gene encodes a protein generates sperm-producing testes.
If there isnt a Y gene no SRY protein is made so the embryo develops egg-production ovaries.
Secondary sex determination
Traits that are caused by the autosomes and it controls the actions of hormons.
Hemizygous
Only having one cope of each allele for a given trait.
Sex linked inheritance
Pattern of inheritance characteristic of genes located on the sex chromosomes of organisms having a chromosonal mechanism for sex determination.
Which organelles carry genetic material
Mitochondria, plastids, and nucleus.
Transforming principle
A mechanism for transfer of genetic information in bacteria in which part DNA from a bacterium of one genotype is taken in through the cell surface of a bacterium of a different genotype and incorporated into the chromosome of the recipient cell, OSWALD AVERY
Hershey-Chase experiemt
Was sought out to determine whether DNA or protein was the genertic materal. Used a virus to attach a bacterium this virus then replicated inside the bacterium. They put radioactive isotopes in the virus one for the protin part the other for the DNA part, once replicated they found DNA was transferred.
DNA
Is a nucleotide, consiting of a sugar deoxyribose, a phosphate group, and a nitrogen containing base. It is cylindrically spiral, it is antiparalle nucleotide bases are on the interior, base pairs are (A-T and G-C)
DNA nitrogen containing bases and how many hydrogen bonds for each.
Purines Adenine and Guanine and pyrimidines cytosine and thymine. A-T having 2 hydrogen bonds. G-C having 3 hydrogen bonds.
Franklin
She prepared crystallographs to see how DNA was shaped
Watson and Crick
Assembled three-dimensional representations, they determined DNA was helical, and density measurment and previous model building resulted in two polynucleotide chains in the molecule, also found DNA is anti parallel.
DNA polymerase
Any group of enzymes that catalyze the formation of DNA strands from a DNA template
Template
A molecule or surface on which another molecule is synthesized in complementary fusion
Nucleoside
A nitrogen base attached to a sugar
Semiconservative replication
Dna is reproduced this way, it is when each parent strand serves as a template for a new strand. The two new DNA molecules each have one old and new strand.
Meselson-Stahl experiment
They devised a simple way to prove the point that DNA is a semiconservative replication, they did density labeling. mixing two types of DNA one more dense than the other, once replicated the DNA was medium density meaning the new DNA had one strand from the dense strand and one strand from the less dense strand.
What are the two steps in DNA replication?
The DNA double helix is unwound to separate the two template strands and make them available for new base pairing.
New nucleotides form complementary base pairs with template DNA, they are covalently linked together by phosphodiester bonds, forming a polymer whose base sequence is complementary to the bases in the template strand.
Where are nucleotides added first?
They are added to the growing new strand to the 3’ end. Movement of addition is 5’ to 3’
dNTP
Deoxyribosnucleoside triphospahte each consist of a nitrogen base attached to deoxyribose, which is then attached to three phosphate groups.
Replication complex
The close association of several proteins operating in the replication of DNA, four proteins.
Origin of replication (ori)
DNA sequence at which helicase unwinds the DNA double delix and DNA polymerase binds to intiate DNA replicated
Primer
Used to start the DNA replicateion it is usually a short single strand of RNA.
Primase
An enzyme that catalyzes the synthesis of one nucleotide at a time to the DNA template.
Which DNA polymerases are responsible for catalyzing most replication
DNA polymerases Delta and Epsiolon
DNA helicase
Enzyme uses energy from ATP hydrolysis to unwind and separate the strands.
Single strand binding proteins
Bind to the unwound strands to keep them from reassociating into a double helix
Replication fork
Sit where DNA unwinds to expose the bases so that they can act as templates
Leading strand
It is the new developed strand, it grows continuously at its 3’ end as the fork opens up. 5’ to 3’
Lagging strand.
It is the other new strand and its oriented so that as the fork opens up, its exposed 3’ end gets farther and farther away from the fork, and an unreplicated gap is formed. Formes in the opposite direction from where the fork is moving.
Okazaki fragments
It is the lagging strand. New stretches of DNA with gaps. It requires multiple primers after each gap. DNA polmerase 3 synthesizes an okanzaki fragment by adding nucleotides to one primer until it reaches the primer of the previous fragment. Then Dna polymerase 1 removes the old primer and replaces it with DNA. Leaving behind a tiny nick. The enzyme DNA ligase links the fragments making the lagging strand whole.
what are telomers
Repeated DNA sequeces at the ends of eukaroyitc gene cycle.
What is the sequence of telopmers
TTA GGG
What are telomers for?
They repeat TTA GGG sequence so that they prevent the DNA repair system from recognizing the ends as breaks.
How are Telomers replicated
It uses an enzyme called telomerase, and it catalyzes the addition of any lost telomerase contains an RNA sequence that acts as a template for the telomeric DNA repeat sequence.
How many DNA repair mechanisms do cells have and what are they?
3, proofreading, mismatch repair, and excision repair
What is proofreading mechanism?
DNA polymerases perform it and each time they introduce a new nucleotide in a growing DNA strand, it proofreads it and takes out the wrong nucleotide and tries again.
Mismatch base repair
A mechanism that scans DNA after it has been replicated and correxts it. Taes out the mismatches base and the adjacent bases then DNA polymerase fixes it.
Excision repair
Removes abnormal bases that have formed because of chemical damage and replaces them with functional bases.
Model organisms
Easy to grow in labs or green houses, and use them for gentics.
Mendel used
Pea plants (pisum sativum)
Ribosomes are composed of
Dozens of proteins and four rRNA molecules
Morgan used
Drosophila (fruit flies)
Meselson and stahl used
E coli.
Beadle and tatum used
Neurospora, bread mold.
Beadle and tatum
Hypothesized that the expression of a specific gene results in the activity of a specific enzyme( one-gene, one-enzyme)
Mutagen
Something known to cause mutations.
One gene one polypeptide
The actual things used in modern day, Function of a gene is to inform the production of a single specific polypeptide.
Beadle and Tatums study
Mutations in bread molds led to our understanding of the one gene one polypeptide relationship.
Transcription
The information in a DNA sequence( a gene) is copied into a complemtary RNA sequence
Translation
This RNA sequence is used to create the amino acid sequence of a polypeptide
Central dogma
The premise that information flows from DNA to RNA to a polypeptide
RNA
Ribonucleic acid, it is an informational polynucleotide that consists of one polynucleotide strand. Nitrogenous bases are adenine, guanine, cytosine, and curacil
Messenger RNA
mRNA carries a copy of a gene sequence in DNA to the site of protein synthesis at the ribosome
Transfer RNA
tRNA carries amino acids to the ribosome for assembly into polypeptides
Ribosomal RNA
rRNA catalyzes peptide bond formation and provides a structure framework for the ribosome.
Codons
Three nucleotides in messenger RNA that direct the placement of a particular amino acid into a polypeptide chain
Transcript
The mRNA copy of the gene
Aniticodon
The three nucleotides in fransfer RNA that pair with complementary triplet( a codon) in messenger RNA
The messenger hypothesis and the adapter hypothesis
A gene is transcribed to produce an mRNA molecule that is complementary to one of the DNA strands, then the tRNA molecules translate the sequence of codons in the mRNA into a sequence of linked amino acids, to form a polypeptide.
Which components are needed for transcription
DNA template for complementary base pairing, one of the two strands of DNA
Appropriate nucleoside triphosphates (ATP,GTP,CTP, and UTP) to act as substrates
RNA polymerase enzyme
What does transcription produce
mRNA,tRNA and rRNA
What are the 3 steps in transcription
initiation, elongation, and termination
Initiation in transcription
Transcription begins with this it requires a promoter( a DNA sequence to which RNA polymerase binds to initiate transcription). The promoters tell RNA polymerase where to start transcription, and which strand of DNA to transcribe. Part of each promort is the initiation site where transcription begins.
Elongation in transcription
Once RNA polymerase has bound to the promoter it begins elongation. RNA polymerase unwinds DNA, then RNA polymerase adds new nucleotides to the 3’ end of the growing strand. The new RNA elongates from the first base which forms its 5’ end to its 3’ end
Termination in Transcription
It is the end of transcription
Genetic code
Set of instuction, in the form of nucleotide triplets, that translate a linear sequence of nucleotides in mRNA into a linear sequence of amino acids in a protein
Start codon
AUG the initation signal
Stop codon
UAA, UAG, UGA termentation signals for translation. the polypeptide is realeased from the translation complex
The DNA chart important fact which was is it read
It is read from the 5’ to the 3’
Transcription and translation in prokaryotes
In the cytoplasm
Transcription and translation in eukaryotes
Transcription in the nucleus, translation in the cytoplasm
Introns
non coding base sequence
Exons
Coding base sequence in eukaryotes
Pre-mRNA
Primary transcript initial gene transcript before it is modified to produce functional mRNA
Processing of pre-mRNA
Two steps in the pre mRNA take place in nucleus. A G-cap is added to the 5’ end, it facilitates the binding of mRNA to the ribosome for translation. Poly A tail added to the 3’ end of the pre-mRNA at the end of transcription, this acts as a signal for an enzyme to cut the pre mRNA immediately after this. Another enzyme adds adenic nucleotides to the 3’ end of the pre mRNA
