cumulative final review Flashcards
1: why is virus sometimes considered living, and sometimes not?
virus is an obligate parasite (not on tree of life)
1: evolution of drug resistance in HIV
random mutations create variations in AZT resistance
high rate of mutation due to reverse transcriptase enzyme
1: characteristics of scientific theory
must be both testable and falsifiable (some possible observation or experimental finding could prove the theory to be wrong)
1: evolution is variational/transformational?
variational: populations evolve, individuals do not.
change through time
change over a long period of time. allele frequencies in a population change from one generation to the next. (due to environmental pressures?)
common ancestry
all life is related through common ancestry
speciation
creation of a new species. species can reproduce with viable, fertile offspring
gradualism
species evolve through slow continuous changes without significant interruption
natural selection
organisms that are better fitted to their environment are more likely to survive and pass on their genes to their offspring.
G1 phase
period of growth before DNA replicates. gap where no DNA is synthesized, cell continues to function
S phase
DNA replication and chromosome duplication occur. continues synthesis of other cellular molecules
G2 phase
second gap where cell growth continues and cell prepares for mitosis. no DNA synthesis, continues to synthesize RNAs and proteins. marks the end of interphase
G1-S checkpoint
before replication, ensures mutations are not duplicated, if severe DNA damage then cell proceeds to G0 phase
G-M checkpoint
ensures that cell is prepared for mitosis. all necessary conditions are met to prevent errors in chromosomes segregation and cell division
mitotic spindle checkpoint
ensures equal distribution of sister chromatids to minimize the risk of aneuploidy
2: positive regulation
phosphorylation cascade - cyclins and CDKs
cyclin binds to CDK
cyclin-CDK complex is phosphorylated
activated cyclin-CDK complex phosphorylates target protein
phosphorylated target protein changes to active form. moves cell into next stage of cell cycle
2: negative regulation
p53 detects DNA damage and increases p21 (cyclin-CDK inhibitor) production which blocks phosphorylation of cyclin CDK. stops cell cycle
2: why is meiosis I reductional and meiosis II equational?
meiosis I: 2n → n
meiosis II: n →n
2: mechanisms giving rise to variation in meiosis
homologous recombination - crossing over at the chiasma
independent assortment - dependent on equatorial arrangement
random fertilization - any haploid cells could fuse
aneuploidy
abnormal number of chromosomes
2: products of life cycle in animals
zygote (2n) → animal (2n) (mitosis)
animal (2n) → gametes (n) (meiosis)
2: products of life cycle in plants and fungi
zygote (2n) → sporophyte (2n) mitosis
sporophyte (2n) → spores (n) meiosis
spores (n) → gametophyte (2n) mitosis
2: products of life cycle in fungi and algae
zygote (2n) → spore (n) meiosis
spore (n) → gametophyte (n) mitosis
gametophyte (n) → gametes (n) mitosis
3: n-value and coefficient of n
n-value: number of unique chromosomes present in an organism
coefficient of n (ploidy): number of unique sets present in an organism
3: C-value and coefficient of C
C-value: amount of DNA in one set of chromosomes, genome size
coefficient of C: how many time the entire genome is present in a cell
3: correlation between n and C, implications on complexity?
n and C are not correlated nor do they dictate complexity in an organism
semi-conservative DNA replication
old strand is template for synthesis for new strand.
cell senescence
irreversible cell cycle arrest. G0 phase, no longer replicates or divides
Hayflick limit
number of times a cell divides before cell division stops
3: mechanism of telomerase action
telomerase restores length of telomeres.
3: why do only cancerous and germ cells express telomerase?
telomerase could cause a problem in somatic cells (mutations)
4: types of DNA damage
exogenous, endogenous
4: exogenous DNA damage
outside, from environment, damages DNA directly.
UV light, chemicals (smoking medication, air pollution), ionizing radiation
4: endogenous DNA damage
inside cell
ROS, replication errors
4: mechanism of ROS
IR splits H2O
very unstable and electronegative
steals electrons → damage to cell
oxygen paradox
repaired by NHEJ
4: mechanism of proofreading
DNA polymerase III corrects itself (exonuclease activity)
4: mechanism of mismatch repair
mismatch repair proteins detect errors and excise and correct incorrect nucleotide
4: mechanism of NHEJ
non-homologous end joining.
repairs double strand breaks
could introduce errors → mutation
4: types of point mutations (3)
substitution: single nucleotide is replaced by another
silent - no effect on amino acid sequence
missense - changes one amino acid, potentially affecting function and structure of protein
nonsense - introduces stop codon leading to truncated polypeptide
4: frameshift mutations (2)
insertion or deletion - addition or removal of nucleotides alters genetic sequence. often leads to truncated protein
4: chromosomal mutations (2)
inversion - segment of chromosomes is reversed in orientation, potentially disrupting gene function
translocation - segments of DNA are exchanged between non-homologous chromosomes, potentially disrupting gene expression
4: thymine dimers
distort the backbone and halt DNA polymerase (not a mismatch)
caused by UV, repaired by excision repair in humans and by photolyase and white light in other species
4: role of tautomeric shifts in mutagenesis (process where DNA changes resulting in a gene mutation
normal pairing favoured, has different preferred partner when tautomeric form shifts. can result in mutation
4: transposable elements
portion of genome that copy/cut and paste somewhere else
4: regulatory role of transposable elements
responsible for increases in genome size.
4: genome composition
55% transposons, viral sequences, dead genes (junk)
25% unknown (junk?)
10% essential (2% coding)
10% intron (junk)
5: epistasis and how it differs from Mendelian genetics
expression of one gene masks the expression of another gene at a different locus. results in complex inheritance patterns that do not conform to the simple dominance and recessiveness observed in classics Mendelian genetics
6: genotypic frequency
distribution of genotypes in a population
6: allele frequency
distribution of a specific allele in a population