Biology Flashcards
Semi conservative replication
2 DNA strands unzip and each are a template for complementary nucleotides to form new strands ( 2 identical chromosomes)
Topoisomerases
Relax supercoiling
Helicase
Disrupts H-bonds between bases which unzips DNA
DNA primase
Forms short RNA primer which initiates binding of DNA polymerase to parent strands
DNA polymerase
Binds to parent strand and travels 5’ to 3’
Parent strands are antiparallel which means?
DNA polymerases want to go in opposite directions
Leading strand is synthesized __________?
Continuously
Lagging strand is synthesized in ___________?
Okazaki fragments ( 200-2000 base pairs separated by 50 base pair gaps )
Ligase fills gaps between __________?
Okazaki fragments
_______________ replaces RNA primer with DNA nucleotides
Another DNA polymerase
DNA
Single origin of replication and 2 replication forks move in opposite directions around chromosome
Eukaryotic DNA
Multiple linear chromosomes sopercoiled around histone proteins, multiple origins of replication
Telomeres
Numerous at ends of eukaryotic chromosomes and prevent damage to coding regions
________ lost from ends of chromosomes with each replication
1
When the last telomere is lost, more replication causes chromosome damage which is associated with?
Aging
Centromere
Area of a eukaryotic chromosome with repeating bases
__________ remain connected at the centromere until disjunction in mitosis or meiosis
2 sister chromatids
Okazaki fragments are much shorter in eukaryotes because of differences in ______?
Polymerases
Transcription ______ to ______?
DNA to RNA
Translation ______ to __________?
RNA to amino acids sequence of proteins
______ of genome transcribed
Only a fraction
Transcribed section of genome?
Gene
Adjacent genes expressed together? (name)
Operon
3 steps of Transcription?
Initiation, Elongation, and Termination
Transcription: Initiation
Transcription factors bind to the promoter site (TATA box) at start of gene
___________ binds to a protein initiation factor to be activated
RNA polymerase
Transcription: elongation
Helicase unwinds gene from nucleosome (histones) and unzips
RNA polymerase disrupts __________ between base pairs
H- bonds
RNA polymerase travels
3’ to 5’
Transcription: termination
RNA polymerase reaches terminator poly-A sequence, releases primary mRNA transcript
Prokaryotes: mRNA translated to ________ by____________ in__________ ?
Protein
Ribosomes
Cytoplasm
Eukaryotes: mRNA posttranscriptionally modified by________?
miRNA
5’ ___________ added to 5’ end of the _________________
Poly-A tail added to __________end
Guanine cap.
Primary transcript
3’
snRNPs
“snurps”
Small nuclear ribonucleoproteins 
miRNA
microRNA
Spliceosomes
Large ribonucle o protein complexes with RNA loops, assembled from snRNPs and proteins
Introns
X
Exons
X
98% of human genome is _________________
Noncoding sequences
Noncoding sequences: __________, __________, and __________
Regulate gene expression
Are transposons (jumping genes)
Have no known function
tRNA, rRNA, and other small regulatory or catalytic RNAs are NOT ________________
Translated
Every 3 nucleotides in mRNA
Codon
Each codon codes for an __________?
Amino acid
Short RNAs, form 3 loop Cloverleaf structure and at the end of the middle loop is an anti-codon
tRNA
Determines amino acid attachment to tRNA, and complementary to mRNA codon
Anti-codon
tRNA is transported to___________?
Cytoplasm
Enzymes attach specific__________________ to each tRNA
Amino acid
Complex protein/RNA structures that catalyze translation of the nucleotide sequence of mRNA into amino acid sequence of proteins
Ribosomes
Composed of two subunits, one large and one small, made of RNA and proteins
(Subunits transcribed and assembled in nucleus and then exported to ER or cytoplasm)
Ribosomes
Ribosomes: small subunit binds to ________________?
mRNA
Ribosomes: large subunit, 3 active sites ?
A : binds to 1st Aminoacyl tRNA
P : binds to 2nd tRNA by peptide binds
E : where 1st tRNA exits
Translation:
3 steps - ___________ ,__________, & ___________
Initiation
Elongation
Termination
____________ : small ribosomal subunit binds 5’ end of mRNA -> initiator tRNA binds to AUG mRNA start codon -> large ribosomal subunit binds to small subunit, with initiator tRNA in the “P” site of the ribosome
Initiation
__________ : new tRNA (complementary to 2nd codon) binds in “A” site of ribosome -> ribosome shifts 3 base pairs toward 3’ end of mRNA -> “P” site tRNA is ejected and a peptide bond forms between the 1st and 2nd amino acids -> 2nd tRNA is now in “P” site with a dipeptide attached -> new tRNA binds to “A” site -> elongation repeats itself
Elongation
__________ : ribosome reaches stop codon -> protein release factors bind to codon and release polypeptide -> ribosome disassemble
Termination
__________ : cleave initiator methionine ; cleave preproteins into polypeptides or add ligands (glycosylation, methylation, phosphorylation)
Posttranslation protein modification
_____________
- “words” in DNA/RNA language
- translated into amino acids, the protein language
- 3 nucleotides long with 4 bases
- 4^3 or 64 possibilities
Codons
________________
- complementary to DNA codons (except U replaces T)
mRNA codons
The 3 stop codons ________, ________, & ________.
- trigger end of translation and ribosomal separation
- do not bind to amino acids
UAA
UAG
UGA
______ (#) tRNAs bind specifically to one of 20 amino acids
61
________________
- evolution favors genetic code in which changes in 3rd base position do no result in a change in amino acid sequence (protects from nearly 1/3 of possible mutations)
- example GAU, GAC, GAG, & GAA all code for alanine
Redundancy in genetic code
________________
single base deletions/insertions can cause transcription frame shift -> entire gene past the mutation no longer codes for the correct protein
Reading frame mutations
Genes are regulated through ________ feedback (activation or induction) or ________ feedback (repression)
Positive
Negative
Switching __________ on/off is key to development and differentiation
Genes
____________ is a sequence of DNA containing a cluster of genes under the control of a single promoter
- gene regulation in prokaryotes
- promoter region, operator region, and several genes related to a particular pathway
Operon
__________ is binding site for RNA polymerase in Operon
Promoter
__________ is on/off switch in Operon
Operator
______ operon (E.coli lactose digestion
positive feedback
repressor protein binds to operator -> lactose binds repressor protein, altering its shape -> releasing protein from operator -> RNA polymerase transcribes lac operon genes -> when lactose is gone, repressor rebinds to operator halting expression
lac
________ operon (enzymes to synthesize tryptophan)
negative feedback
repressor protein binds to operator when it combines with tryptophan (when tryptophan is abundant)
trp
Acetylation of histones in nucleosome cause DNA to _________
- genes can be expressed
Uncoil
Deacetylation/Methylation os histones causes DNA to __________
- stop genes expression
Supercoil
____________
- proteins bind to promoter to start transcription
Transcription factors
____________
- DNA sequences that interact with promoter to allow expression
Control elements
Groups of control elements are called __________
enhancers
____________ bind enhancers and transcription factors which form initiation complex with RNA polymerase at promoter
Mediator proteins
____________ bind near the promoter, preventing the initiation complex or RNA polymerase binding
Repressor proteins
____________
- increases gene expression
- plays critical role in evolution because one version can remain intact while the other changes (genetic drift)
Gene duplication
____________ can interfere with transcription or mRNA to stop translation
small noncoding RNAs
____________
a DNA molecule coiled around histone proteins (chromatin)
Eukaryotic chromosome
Human chromosome has about ____________ million base pairs (bp)
50 - 250 million
____________
about 200 base pairs wrapped around each histone
Nucleosome
____________
- uncoiled areas of a chromosome
- active gene expression
- light colored in stained microscope images
Euchromatin
____________
- DNA tightly supercoiled
- darkly stained (microscope images)
Heterochromatin
____________
- repetitive noncoding DNA at ends of each chromosome
- protect coding regions from damage over time
Telomeres
____________
- DNA sequences
- stay connected after replication
- hold 2 sister chromatids together until disjunction in mitosis or meiosis
Centromere
____________
- fibers attach to the chromatids at the centromere
Kinetichore
______________________
- alteration of naturally occurring genomes in organisms for medical, pharmaceutical, agricultural, environmental, or general research purposes
- genes isolated from one species or novel genes used to transform another species
- human insulin gene was inserted into E.coli to create insulin-producing bacteria
Recombinant DNA technology
(biotechnology, genetic engineering or modification)
____________
- inserting foreign DNA into a plasmid (extrachromosomal DNA) or bacteriophage virus -> transforms the bacteria
- genes of interest linked to a marker (ex: antibiotic resistance, phosphorescence)
-inserting foreign DNA into the plasmid or viral genome uses restriction enzymes which cleave DNA at specific sequences where the ends of segments are offset by several bases -> projecting bases (sticky ends) reanneal with foreign DNA in the plasmid or viral DNA
Bacterial transformation
____________
- use different restriction enzymes to cut genomes into segments -> separated by electrophoresis -> used to locate/isolate specific genes
DNA libraries
____________
- made using reverse transcriptase & DNA polymerase to make DNA from mRNA
- a specific cDNA library reflects proteins synthesized by a cell at that stage in the cell cycle, a step in proteomic research or to isolate specific genes
cDNA
____________
- used to clone/amplify DNA sequences
- requires primers (complementary to 3’ ends of target strands
- primers facilitate polymerization
- DNA is heated, polymerized, reheated, and repolymerized, doubling the DNA each time
PCR
____________
- spliced next to a promoter region to assure their expression in host cells
cloned genes
____________
- having 2 copies of the genome
- zygotes
- somatic cells
diploid
____________
- having one copy of the genome
- gametes
haploid
____________
- unit of heredity
- sequence of DNA
- codes for protein or nontranslated RNA
Gene
____________
- one of several variants of a gene
- results from inherited mutations of a gene
Allele
____________
- outward expression of a trait
- morphological, physiological, or behavioral
Phenotype
____________
- the actual combination of possible alleles of a gene
genotype
____________
- having 2 identical alleles of a gene
homozygous
____________
- having 2 different alleles of a gene
heterozygous
____________
- position of a gene on a chromosome
locus
____________
- all the genes in an individual of a species
genome
____________
- all the alleles of a gene or set of genes in a population
gene pool
____________
- shows in phenotype when homozygous or heterozygous
dominant
____________
- expressed only if there are 2 of the recessive alleles
recessive
____________
- heterozygotes show distinct or intermediate phenotype
Incomplete dominance
____________
- both alleles expressed
- ex: ABO blood groups (AB blood)
Codominance
____________
- degree to which genotype is expressed in the phenotype of a fraction of population with that genotype
- ex: 50-70% women with BRCA1 mutation develop breast cancer
Penetrance
____________
- degree of phenotype variation among individuals with same genotype
Expressivity
____________
- a single gene affecting several traits
Pleiotropy
____________
- 1 gene influencing the phenotype of another gene
Epistasis
____________
- Mendel noticed that results of monohybrid crosses were always a 3:1 dominant:recessive ratio
- concluded that each trait was controlled by 2 copies of a gene and gametes randomly receive 1 copy of each gene
Random segregation
____________
- 9:3:3:1 phenotypic results of dihybrid crosses involving 2 heterozygous traits
- concluded genes on separate chromosomes sort independently
Independent assortment
____________
- loci on the same chromosomes that do not sort independently
linked genes
____________
- sections of DNA from 1 chromosome crossover to its homologue, altering predicted ratios by changing linkage patterns
Recombination
____________
- males inherit X chromosome from mother and Y chromosome from father
- males inherit X cannot be heterozygous for sex-linked traits
Sex-linkage
____________
- extranuclear inheritance
- inherited matrilineally
mitochondrial genes
____________
- diploid eukaryotic cell division to produce 4 haploid gametes
meiosis
____________
- in diploid cell, replicated homologous pairs unite in synapse -> from tetrads comprised of 4 chromatids, connected by synaptonemal protein complex -> recombination, trading segments of paternal and maternal homologues can occur -> homologous chromosomes separate -> cell divides, forms 2 haploid cells
1st meiotic division
____________
- replicated chromosomes line up individually along equator -> chromatids are pulled apart and the resulting cells for 1n gametes
2nd meiotic division
____________
- eukaryotic cell divides, forming identical 2n cells
- replicated chromosomes line up singly at equator of cell -> chromatids disjoin -> cytokinesis form daughter cells
- reproduction in unicellular eukaryotes
- growth & repair in multicellular eukaryotes
Mitosis
Cell Cycle : ________, ________, ________, ________, & ________
Interphase
Prophase
Metaphase
Anaphase
Telophase
____________
- in breeding experiments, normal traits without induced mutations
Wild type
____________
- between 2 individuals heterozygous for a gene
- results in 1:2:1 genotypic and 3:1 phenotypic ratios in simple dominance genes
- incomplete dominance traits yield a 1:2:1 ratio for both genotype and phenotype
monohybrid cross
____________
- parents heterozygous for 2 unlinked genes
- 9:3:3:1 phenotypic ratio
dihybrid cross
____________
- a cross between a dominant individual of unknown genotype with a known recessive (if any recessive offspring, dominant parent must be heterozygous
testcross
____________
- breeding offspring with parent to retain desirable phenotypes
backcross
____________
- rates of recombination determine distances between linked genes
- restriction enzyme library hybridization provides more detail
- genome sequencing provides most detail
gene mapping
____________
- analysis of a trait through multiple generations
pedigree analysis
____________
- statistically determines allele frequencies in population
Hardy -Weinberg equilibrium
Hardy-Weinberg equilibrium conditions include, ________, ________, ________, ________ & ________ (prevent population from evolving)
-if 1 or more conditions not met then population undergoes microevolution (change in allele frequencies)
large population
random mating
no natural selection
no mutation
no gene flow
____________
- biometric statistical methods determine allele frequencies for multiple-allele genes or polygenic traits
quantitative genetics
Hardy-Weinberg equilibrium
p =
q =
p^2 =
2qp =
q^2 =
__ + __ =
__ + ___ + __ =
p = frequency of dominant allele
q = frequency of recessive allele
p^2 = frequency of homozygous dominants
2qp = frequency of heterozygotes
q^2 = frequency of homozygous recessives
p + q = 1
p^2 + 2qp + q^2 = 1
____________
- fundamental unit of life capable of carrying out all life functions
Cell
____________
- cytoplasm, cell membrane, single circular chromosome, ribosomes
- Often cell wall, flagella, or other external structures
- Bacteria and Archaea
- Unicellular
Prokaryotes
____________
- complex cells, numerous internal membrane-bound organelles, multiple complex chromosomes contained inside nucleus
- Animals, Plants, & Fungi
Unicellular & Multicellular Species
Eukaryotes
_______________
- earliest eukaryote engulfed or was invaded by smaller prokaryote which continue to function inside host cell, conferring higher fitness
- Explains evolution of eukaryotes, based largely on evidence from mitochondria and chloroplasts, which contain their own DNA and ribosomes similar to those found in prokaryotes
Endosymbiosis
_______________
- viscous, intracellular medium
- ~70% water
- Biochemical/mineral solutes
Cytoplasm
_______________
- composed of RNA and protein
- sites of proteins synthesis (mRNA translation)
- suspended and cytoplasm are embedded in ER or other internal membrane
Ribosomes
_______________
- phospholipid bilayer
- hydrophilic on both internal and external cell surfaces
- hydrophobic in the membrane interior
- contains cholesterol & proteins
Plasma membrane
_______________
- double membrane
- Contains DNA and regulatory proteins
Nucleus
_______________
- inside nucleus
- site of rRNA synthesis and ribosome assembly
Nucleolus
_______________
- aerobic cellular respiration
- Double membrane structure
- Krebs cycle occurs in matrix
- Electron transport chain proteins embedded in inner membrane
Mitochondria
_______________
- breakdown cellular waste for export and provide digestive function
- Acidic and filled with digestive enzymes (from Golgi body)
Lysosomes
_______________
- convoluted membrane network, dotted with ribosomes
- New peptide has short amino acid sequence that signals chaperone proteins to move the peptide to destination for folding, modification, activation, & export
Rough endoplasmic reticulum (RER)
_______________
- lipid and carbohydrate anabolism
- Ca2+ balance
- detoxification
Smooth endoplasmic reticulum (SER)
_______________
- modifies/packages proteins for export or intracellular delivery
Golgi body
_______________
- oxidative enzymes catalyze fats/toxins
Peroxisomes
_______________
- proteins provide support, shape, intracellular, transport, so motility, cell adhesion, etc.
- Microfilaments (actin) change cell shaped
- Intermediate filaments secure the cytoskeleton, help in cell transport and cell adhesion
- Microtubules (large hollow protein tubes) parts for motor proteins to transport organelles & rearrange shape for division
Cytoskeleton
_______&________
- composed of microtubules attached by basal body
- motility
Cilia
Flagella
_______________
- govern reorganization of cytoskeleton in division
- similar to basal bodies
Centrioles
_______________
- small unchanged molecules and hydrophobic molecules diffuse through membrane
- Ions and larger
- Polar molecules cannot penetrate
Semipermeable plasma membrane
_______________
- due to random movement of molecules
- No energy input
Passive transport
_______________
- movement of solutes in fluid from higher to lower concentration
Diffusion
_______________
- diffusion of water across membranes from hypotonic to hypertonic
Osmosis
_______________
- through transmembrane channel/carrier proteins
- by molecules that cannot permeate membranes
Facilitated diffusion
_______________
- movement of molecules that requires expenditure of ATP energy
Active transport
_______________
- transport substances, through a membrane against a concentration gradient
- Na+/K+ pump
- Proton pump
Pump proteins
_______________
- engulf or expel dissolved substances or particles
Bulk transport (Endocytosis/exocytosis)
_______________
- connexon proteins embedded in plasma membranes of cells, conduits between the cytoplasm of each cell
- ex: allow cardiac cells to coordinate contraction
Gap junctions
_______________
- membrane proteins anchored to Microfilaments cement cells together to form a continuous impermeable surface
- ex: blood brain barrier
Tight junctions
_______________
- proteins hold cells together, form tissues
- interstitial fluid between cells
Desmosomes
3 types of cell-to-cell communication
_______________
_______________
_______________
Juxtacrine signaling
Paracrine signaling
Endocrine signaling
_______________
- Chemical or charge potential communication
- Uses direct cell contact through gap junctions or desmosomes
Juxtacrine signaling
_______________
- Chemical signals between cells in close proximity
- ex: Neurotransmitters between neurons and effector cells
Paracrine signaling
_______________
- Chemical signals via blood
- Cells distant from each other
Endocrine signaling
_______________
- 40% of all cells
- Lines the exterior of body, walls of body openings, body cavities, & glands
- regulates passage of materials into or out of the tissue
- Lubricates with secretions
- Protects from abrasion by rapid regeneration
- Secretes basement membrane of lycoprotein/collagen
Epithelial tissue
Epithelial tissue:
Single layered = __________
Multi layered = __________
Flat = _________
Cubed = __________
Column = _________
Simple
Stratified
Squamous
Cuboidal
Columnar
_______________
- most abundant tissue type
- Forms bones, tendon, ligaments, blood, fat, underlying skin layers, and interstitial matrix (between organs/other structures)
Connective tissue
Connective tissue is derived from _______________
- differentiates to cell types of blood cells, fibroblasts, adipocytes, chondrocytes, osteocytes, macrophages, mast cells
Embryonic mesenchyme
The connective tissue secretes ___________ made of proteins, polysaccharides, & glycoproteins
Extracellular matrix
3 principles of cell theory
_______________
_______________
_______________
- All living organisms are composed of one or more cells.
- Cells are fundamental living things (viruses/organelles are not considered living)
- All cells are products of reproduction of pre-existing cells.
____________ first recognized cells
‘Robert Hooke
_______________ observed cellular reproduction, and questioned spontaneous generation of life
Anton von Leeuwenhoek
____________ was formulated by Schwann, Schleiden, & Virchow in 1830s although the 3rd principle was not fully accepted until Pasteurs experiments in 1850s
Cell theory
_______________
- 2 domains (Archaea & Eubacteria)
- all Unicellular
- Aerobic or anaerobic environments
- Autotrophs or heterotrophs
- Mostly pathogenic or symbiotic species
Prokaryotes
Prokaryotes Classification :
Shape
Spherical = __________
Coccus
Prokaryotes Classification :
Shape
Rod = __________
Bacillus
Prokaryotes Classification :
Shape
Spiral = __________
Spirillus
Prokaryotes Classification :
Grouping
Pairs = __________
Diplo
Prokaryotes Classification :
Grouping
Chains = __________
Strepto
Prokaryotes Classification :
Grouping
Branched clusters = ____________
Staphylo
Prokaryotes Classification :
Cell Wall
____________ have thick peptidoglycan cell walls, & appear stained purple
Gram-positive
Prokaryotes Classification :
Cell Wall
__________ have thin peptidoglycan layer between 2 membranes, and appears stained red/pink (most serious pathogens because lipopolysaccharides on outer membrane’s act as powerful toxins)
Gram-negative
Prokaryotes Classification :
Metabolism
Cannot survive without O2 = ____________
Obligate aerobes
Prokaryotes Classification :
Metabolism
Cannot tolerate O2 = ____________
Obligate anaerobes
Prokaryotes Classification :
Metabolism
Respire with or without O2 = ____________
Facultative anaerobes
____________________
- some prokaryotes produce a protective glycoprotein or carbohydrate capsule around their cell walls
- In some bacteria this forms an adhesive Biofilm
Glycocalyx
____________________
- a thick protein structure protects from adverse conditions
Endospore
____________________
- thin protein filament that helps a bacterium attach to a substrate or host cell
Fimbrae
____________________
- many move using one or more of the structure
- a thin protein filament attached to a spinning base unit
- differs in structure in mechanics from eukaryotic type (which whip back and forth)
- Bacteria can reverse direction by reversing spinning
Flagella
____________________
- mutations that confer resistance
Antibiotic resistance
____________________
- prokaryotes that reproduce as quickly as every 20 minutes
- The rapid reproduction rate, along with a constant rate of mutation, make bacteria, highly adaptable
Adaptability
____________________
- are the most ubiquitous organisms on earth, occupying all possible habitats
Prokaryotes
____________________
- prokaryotic DNA, circular molecule attached to plasma membrane in the Nucleoid Region
- Transcription and translation occur simultaneously in the cytoplasm
Simple genomes
____________________
- small, circular, extragenomic DNA molecules present in the cytoplasm of prokaryotes
- Often contain genes that confer antibiotic resistance
Plasmids
____________________
- in prokaryotes, plasmids may spliced into or out of the genomic chromosome
- this process is mimicked in use of plasmids in biotechnology (recombination)
Transposons
____________________
- cell division in prokaryotes, simple and rapid
- DNA replicates than the cell divides (starting from a single origin of replication)
Binary fission
____________________
- tubular proteins structures protruding from the prokaryotic cell
- Function in cell-cell interactions, and as a conduit for transduction (the exchange or transfer of a copy of a plasmid from one bacterium to another)
Pili
____________________
- proteins encapsulating a small DNA or RNA chromosome
- no metabolic or reproductive processes
- take over metabolic, reproductive mechanisms of host cells
- evolve in response to changes in hosts
- adapt rapidly to immune responses
Viruses
Viruses are classified according to __________ , ____________, & ______________ .
Host type (prokaryote, or eukaryote) - host range
Capsule composition and structure
Nucleic acid type
Viruses outside the host are called ____________ .
Virions
____________________
- protein capsid surrounding DNA
- Complex proteins tail sheath to inject, viral DNA into host bacterium
- Tail fibers bond to bacterial cell wall
Bacteriophage virus
____________________
- misfolded proteins
- enter a host, cause chain reaction of similar proteins misfolding
- Creutzfeldt-Jakob & bovine spongiform encephalopathy are diseases
Prions
____________________
- tiny circular RNAs that infect plants, but do not contain genes
- their presence in a host cell activates RNA silencing mechanisms, halting proteins synthesis
Viroids
____________________
- Insert their nucleic acid into host cells, co-opting cells infrastructure to synthesize viral proteins and genomes, which self assemble and exit to infect other cells
Viruses
Many viruses alternate between __________cycle & __________ cycle
Lytic cycle
Lysogenic cycle
____________________
- complete takeover of the host cell transcription and translation process
- Rapid production of new viruses
- Rupture of host cell releases new viruses
Lytic cycle
____________________
- viral DNA splices into host genome
- cell continues to function, copying, viral genome (prophage) with each division
- Lytic cycle follows
Lysogenic cycle
____________________
- prophage causes harmless bacterium to become pathogenic
Lysogenic conversion
____________________
- viral RNA is translated on entry into cell
Eukaryotic RNA viruses
____________________
- RNA viruses that translate reverse transcriptase, an enzyme that synthesize DNA from RNA
- the DNA can then enter a lysogenic cycle
Retroviruses
____________________
- A retroviral infection that infects specific cells of the human immune system, and causes acquired immunodeficiency syndrome (AIDS)
- Infects helper T cells, dendritic cells, & macrophages
- Helper T cell numbers decline I
- Increase susceptibility to infection & certain cancers
Human immunodeficiency virus (HIV)
HIV is coated with __________ proteins in lipid membrane remaining from past host cell that fuses with new host cell plasma membrane, allowing viral capsid to enter
Docking
HIV inside the host cell (steps)
- viral RNA translated by cytoplasmic ____________
- ________________ catalyzes the synthesis of DNA from the viral RNA template
- ________________ catalyzing splicing of the viral DNA into host cell DNA
- Virus is in __________ phase (hiding) in the host cell genome
- Virus enters __________ phase producing billions of new virions, spreading throughout the hosts immune system
Ribosomes
Reverse transcriptase
Integrase
Latent phase
Lytic phase
____________________
- between and during cell division, cells go through distinct phases
- Generation time
- Time between divisions
- Days in eukaryotes
Cell cycle
____________________
- between cell divisions
- Contains 3 sub phases
Interphase
____________________
- transcription/translation of genes for cell growth/function
G1 phase (1st gap)
____________________
- DNA replication
- Subphase in interphase
S phase (synthesis)
____________________
- similar to G1 but cell division is certain
- mitosis follows this phase
G2 phase (2nd gap)
In cells that undergo growth arrest, terminal division followed by G1 is followed by __________ (cell continues to function but no more growth or DNA replication)
G0
In damaged cells, G2 is followed by ____________
Apoptosis
Transition between sub phases is regulated by a series of cell cycle ____________ , proteins that inhibit or prevent synthesis of enzymes that trigger the next phase.
Checkpoints
____________________
- asexual reproduction of unicellular eukaryotes
- Development, growth, and repair in multicellular eukaryotes
Mitosis
M phase
____________________
- Replicated chromosomes supercoil (characteristic X shape of replicated sister chromatids connected at centromere)
- Nuclear membrane dissolves
- Cytoskeleton rearranges microtubules grow outward from the centrioles to form mitotic spindle
Prophase
____________________
- Centrioles migrate to poles
- Spindle fibers attach to kinetochores of each chromatid
- replicated chromosomes lineup individually at equator
Metaphase
____________________
- disjunction
- Sister chromatids split at centromere and pulled to each pole
Anaphase
____________________
- chromosomes uncoil then nuclear membranes form around 2 nuclei
Telophase
____________________
- Cell contents divide
- Cleavage furrow at equator as plasma membrane pinches into 2 cells
Cytokinesis
____________________
- forms gametes (1n) in sexual reproducing eukaryotes
Meiosis
____________________
- sperm/ova
- haploid (1n)
Gamete
____________________
- diploid (2n)
- homologous pairs of each chromosome
Zygote & somatic cells
A human gamete has _____ chromosomes
A human diploid cell has _____ chromosomes
23
46
Human cells have _____ autosomes & _____ sex chromosome
22
1
____________________
- begins with G2 germ cells in gonads
- consists of 2 cell divisions
Meiosis
____________________
- replicated chromosomes supercoil
- nuclear membrane dissolves
- spindle fibers link centrioles to centromeres
- homologous pairs form tetrads (4 chromatids) and process of synapsis
- recombination (crossing-over) possible at Chiasmata (homologous chromatids intersect)
- exchange bits of maternal/paternal chromatids
Prophase I
____________________
- synapsis continues
- homologous chromosome pairs line up at equator
Metaphase I
____________________
- homologous chromosome pairs are split apart toward poles
Anaphase I
____________________
- reduction division (chromosome number halved)
- cell completes division I
- daughter cells haploid, nonidentical (chromosomes still replicated)
Telophase I
____________________
- similar to mitosis begins with 2 haploid cells
Meiosis II
____________________
- chromosomes supercoil
- Nuclear membrane dissolves
- Spindle forms
Prophase II
____________________
- chromosomes lineup individually across equator
Metaphase II
____________________
- chromatids split into separate on replicated chromosomes (disjunction), pulled toward poles
Anaphase II
____________________
- chromosomes uncondensed
- nuclear membrane forms, followed by cytokinesis
- result is 4 non-identical haploid gametes
Telophase II
____________________
- Spermatogonia line seminiferous tubules ——>
- Testosterone triggers mitosis ——->
- 2n spermatocytes ——->
- Meiosis ——->
- 1n spermatids ——->
- Grow flagellum ——->
- Spermatozoa
Spermatogenesis
____________________
- Oogonia in ovarian follicles, outer cortex of ovary ——->
- Primary oocytes stop in metaphase II before birth ——->
- Post puberty, several follicles undergo oogenesis monthly ——->
- 1 forms of ovum
- oogenesis divisions unequal, all cytoplasm in each division goes to 1 cell ——->
- Forms 3 polar bodies and 1 secondary oocyte ——->
- Becomes ovum upon fertilization
Oogenesis
____________________
- sperm survive up to 5 days in female reproductive tract
- oocyte viable for 12-24 hours
- many sperm reach ovum and uterine tube ——->
- Enzymes break down corona radiata/zona pellucida around oocyte ——->
- 1st sperm to reach oocyte membrane binds sperm receptors ——->
- Ca2+ release prevents additional sperm entry ——->
- oocyte completes meiosis II ——->
- Nuclei fuse to become 2n zygote
Fertilization
____________________
- zygote divides as it passes uterine tube ——->
- Forms blastocyst ——->
- Implants in ovary ——->
- Endometrial capillaries erode ——->
- Exchange nutrients/waste with maternal blood ——->
- Blastocyst hCG causes corpus luteum production of progesterone/estrogen
Implantation
____________________
- fetal/maternal capillaries intertwine ——->
- form placenta (fetal chorionic villi grow into endometrium)
- allantois forms umbilical cord, & connects embryo to placenta
Placentation
True or false:
No contact between maternal and fetal blood
True
Placenta takes oversecretion of progesterone/estrogen by ________
9 weeks
____________________
- ~40 weeks from 1st day of last menstruation
- in 1st 9 weeks the zygote develops into embryo with limbs in early organ systems
- after 9 weeks the fetal development continues until 37-40 weeks
- Earlier birth is pre-term
Gestation (pregnancy)
____________________
- Labor, uterine contractions ——->
- Causes cervical dilation ——->
- Baby exits through vagina ——->
- Placenta separates from uterine wall and exits separately
Parturition (birth)
____________________
- postfertilization, the zygote divides rapidly (cleavage) by mitosis without G1 & G2 stages into a morula (solid ball of progressively smaller cells)
Morulation
____________________
- after 6 - 8 divisions the cells of the Morula flatten, forming a tight sphere of cells (blastula) around a fluid filled cavity (blastocoel)
- blastula contains outer layer (trophoblast) and inner cell mass that becomes embryo and amniotic tissue
- it’s complete by day 7 when implantation occurs
Blastulation
____________________
- ~day 12 the gastrula forms
- cells derived from inner cell mass then divide into 3 germ layers (Ectoderm, Mesoderm, & Endoderm)
- 1 part of trophoblast forms chorionic villi
- 1 part of trophoblast forms archenteron
- a groove (blastopore) in the archenteron becomes anus in deutrostomes
- a groove (blastopore) in the archenteron becomes mouth in protostomes
Gastrulation
____________________
- neural tube development (chordates)
- mesoderm/ectoderm cell signaling interactions cause ectoderm to form neural plate ——-> folds to become dorsal nerve cord
Neurulation
____________________
- 3 primary germ layers differentiate into distinct tissues and organs
Organogenesis
The 3 primary germ layers are :
_______________
_______________
_______________
Ectoderm
Mesoderm
Endoderm
____________________
- Nervous system (also pituitary/pineal glands)
- Integumentary system (mucous membranes/outer layer of skin, mouth, pharynx, anus)
- Epithelial derived structures (hair, follicles, sweat/memory glands, cornea/lens)
- Adrenal medulla
- Neural crest cells migrate to become epithelium and portions of jaw, teeth, and heart valves
Ectoderm
____________________
- Bones/connective tissue ( cartilage, tendons, ligaments, blood, dermis)
- Muscle
- Circulatory, Lymphatic, Reproductive, Urinary systems (blood vessels, spleen, reproductive organs, kidneys, bladder, smooth muscle)
- Adrenal cortex
- along notochord, it forms somites ——-> become vertebral column & muscles of spine & rib cage
Mesoderm
____________________
- respiratory system (epithelia of trachea, bronchi, alveoli)
- Digestive system (epithelia of esophagus, stomach, intestines)
- Liver, Pancreas, Lining of Thymus, Thyroid/Parathyroid
- Epithelial lining of urethra, bladder, & reproductive systems
Endoderm
Zygote is _______________ (differentiates into every cell type)
Totipotent
After 5th division, embryonic morula stem cells are _______________ (into 1 of 3 germ layer tissues)
Pluripotent
Cells later reach determined state, which means?
There is no change to different cell types
____________________
- process of cell specialization
- Determines size, shape, metabolism, membrane, potential, & responsiveness to signals
- these types of cells are genetically identical, but different genes are turned on/off at specific times in development
Differentiation
____________________
- through gap junctions and desmosomes results in asymmetric cell divisions with different genes expressed in daughter cells
- affects gene expression in neighboring cells
- effect diminishes with distance
Juxtacrine signaling
____________________
- occurs at various developmental stages
- cell must detach from its original location and form a protrusion at the leading edge. This protrusion, called a lamellipodium, is formed by the polymerization of actin filaments. The cell then uses this protrusion to push itself forward, while the trailing edge of the cell contracts, pulling the cell forward.
- As the cell moves forward, it interacts with its environment through specialized proteins called integrins, which anchor the cell to the extracellular matrix. The cell also secretes enzymes called matrix metalloproteinases, which help to break down the extracellular matrix and create space for the cell to move through.
Ex : neutral crest cells migrate from neural tube to peripheral sites ——-> differentiate into distinct tissues
Cell migration
____________________
- differentiation of pluripotent stem cells is controlled by regulation of cell cycle, and activation or suppression of specific genes
Embryonic development
____________________
- changes in gene expression in 1 cell affect genes in another
- sets of regulatory genes direct development and differentiation
- growth factors (signaling proteins that cause inductive effects on competent cells)
- transcriptional factors (Hox genes are responsible for cephalization, segmentation
Induction
____________________
- regrowth of damaged tissue
- many differentiated cells cannot normally regenerate (muscle or nerve)
- liver, bone, & skin regenerate readily
Regeneration
____________________
- failure of normal cells to regenerate
- Eventually die
Cellular senescence
____________________
- programmed cell death due to cell damage
- part of normal fetal development & in the postbirth uterus
Apoptosis
____________________
- communication by electrochemical signals
- receives sensory info (sensory neurons) —–>
- processes info —–>
- relays response to muscles, glands, & effector cells
Nervous System
Neuron bundles form __________ nerves
Peripheral Nervous System (PNS)
Neurons & Glia form the networks of the _______________
Central Nervous System (CNS)
____________________
- combination of sensory & motor nerves
- contains Somatic Nervous System & Autonomic Nervous System
Peripheral Nervous System
____________________
- conscious sensation and movement
- includes reflexes
Somatic nervous system
____________________
- unconscious visceral senses such as detection of blood pressure or body temperature & unconscious movement
- heart contraction & peristalsis
Autonomic Nervous System
____________________
- brain/spinal cord processes, integrates, coordinates sensory info & responses
Central Nervous System
____________________
- transmit info to spinal cord/brain (CNS)
- afferent/inward
Sensory neurons
____________________
- transmit info from CNS to muscles/glands (effectors)
- efferent/outward
Motor neurons
Processing of information occurs in _____________ of CNS
Gray matter
- contains the cell bodies
- Appears gray because there is no sheath insulation like axons
_______________ transmits info between parts of brain or between CNS & PNS
White matter
- axons
The autonomic nervous system contains the ____________ & the ____________ .
Sympathetic nervous system and parasympathetic nervous system
____________________
- fight or flight sudden responses
Sympathetic nervous system
____________________
- rest and digest body functions
Parasympathetic nervous system
________________ Nervous System
- Controls digestive function
- Distinct from ANS
Enteric nervous system
____________________
- involuntary response to stimuli
- bypasses cognitive part of brain
- Stimulus info via afferent nerve to spinal cord gray matter (or midbrain for senses above neck) ——->
- Immediate response travels and efferent nerve to an effector
- Monosynaptic reflex arc (receptor—> sensory neuron—> motor neuron—> effector)
- Polysynaptic reflex arc (receptor—> sensory neuron—> CNS interneuron—> Motor neuron—> effector)
Reflex
3 structures of a neuron
__________
__________
__________
Soma (cell body containing nucleus & organelles)
Dendrites (receive stimulus)
Axon (long nerve fiber that branches/terminal buds at the end)
____________________
- part of axon at soma
- Lets signal pass, only if stimulus is sufficient
Axon hillock
____________________
- Gap between axon buds and next neuron
- Paracrine signaling conveys info
Synapse
____________________
- Signal initiated, propagated by opening ion channel —->
- Changes transmembrane electrochemical potential by letting certain ions in/out
Ion channels
____________________
- in dendrites
- Received chemical signal, open from outside
Ligand gated ion channels
____________________
- in the membrane of soma and axon
- Electrochemical signal
- Open from inside by voltage change
Voltage gated ion channels
____________________
- along axon, bulges of white fatty Lipoprotein secreted by certain glia
- Schwann in PNS
- Oligodendrocytes in CNS
Myelin sheath
(lipoprotein =myelin)
____________________
- myelinated nerve impulse is faster, because signal jumps between gaps in myelin
Saltatory propagation
____________________
- gaps between myelin
Nodes of Ranvier
__________ matter = unmyelinated
__________ matter = myelinated
Gray matter
White matter
____________________
- most abundant cells in nervous system
- Nourish, protect, & direct growth of neurons
- differentiate into 3 types : astrocytes, microglia, & ependymal cells
Glial cells
____________________
- glial cell that supports CNS neurons
Astrocytes
____________________
- glial cell that protects CNS from infection
Microglia
____________________
- glial cell that lines CNS cavities
Ependymal cells
____________________
- junction between 2 neurons or neuron & effector cell
Synapse
____________________
- cell conveys signal
- synapse
Presynaptic
____________________
- cell receives signal
- synapse
Postsynaptic
2 types of synapses are __________ & __________
Chemical synapse
Electrical synapse
____________________
- paracrine
- terminal buds of presynaptic axon, synaptic cleft filled with interstitial fluid, & a postsynaptic cell (neuron or effector)
- axon terminals contain vesicles filled with chemical neurotransmitters
- When an action potential arrives at terminal bud, the voltage gated calcium channels open —->
- neurotransmitters cross synapse & bind to postsynaptic cell receptors that trigger continued propagation of the signal —->
- neurotransmitters are digested by enzymes or absorbed by the presynaptic neuron
Chemical synapse
____________________
- juxtacrine
- nerve impulse is directly transmitted from one cell to the next via connexons (proteins channels at gap junctions between cells)
Electrical synapse
____________________
- voltage difference a Crossing Neuroal and Membrane when nerve not transmitting signal
- ATP energy to maintain
- Typically -70mV
- Inside membrane negative relative to outside
- is established by action of Na+/K+ pump
- ATP used to pump Na+ ions outside cell & K+ into cell (3:2 ratio Na:K)
Resting potential
____________________
- dendrites receive stimulus —-> alter membrane potential
- magnitude of change depends on strength of stimulus
Graded potential
____________________
- Na+ channels open, local membrane potential approaches 0 (depolarization)
- Strong enough signal at axon hillock triggers it —->
- Voltage gated Na+ channels, open in sequence down axon —->
- Followed by repolarization due to K+ voltage gated channels opening —->
- Resting potential reestablished by Na+/K+ pumps
Action potential
____________________
- takes ~2 milliseconds at any point on axon
- resting potential restoration (refractory period) takes 2-3 milliseconds more
Depolarization-Repolarization
Nerve impulses elicit either ____________ or ____________ responses in target cells
Excitatory response
Inhibitory response
____________________
- stimulus causes Na+ channels to open —->
- membrane depolarizes —->
- favors action potential, impulse propagation
Excitatory response
____________________
- stimulus opens K+ or Cl- channels —->
- Hyperpolarization —->
- inhibits action potential, prevents signal propagation
Inhibitory response
