chapter 15 - evolution of genes and genomes

Question 1

what is the neutral molecular evolution theory?

Answer 1

the majority of mutations are neutral and may fix in populations through genetic drift
rate of fixation by genetic drift = rate of neutral mutation

Question 2

what is the random walk theory?

Answer 2

for a neutral allele, its frequency in the population is the probability that the allele with reach fixation by genetic drift

Question 3

what is the probability of fixation for a new neutral mutation?

Answer 3

1/2N

where N = #individuals and 2N = # alleles

Question 4

what does the field of molecular evolution entail?

Answer 4

the study of mechanisms and consequences of evolution of macromolecules
the relationships between the structure of genes, proteins, and organism function
using molecular variation to reconstruct evolutionary history

Question 5

define synonymous (silent) mutations

Answer 5

nucleotide substitution in a protein coding region that does not change the amino acid that is specified

Question 6

define a nonsynonymous substitution

Answer 6

a nucleotide substitution that does cause an amino acid change

Question 7

nonsynonymous substitutions may result in:

Answer 7

deleterious effects that affect protein shape/function

OR selectively neutral or beneficial effects

Question 8

T or F: mutations do NOT occur equally at all 3 codon positions

Answer 8

false - mutations occur equally at all 3 positions

Question 9

T or F: synonymous subs occur more frequently than nonsynonymous, despite mutations occurring equally at all 3 codon positions

Answer 9

true

Question 10

probability of fixation is mediated by:

Answer 10

selection relative to phenotypic effects

Question 11

what is the effect on the rate of synonymous and nonsynonymous substitutions if amino acid position is under positive selection for change?

Answer 11

the rate of nonsynonymous subs can be much higher than synonymous

Question 12

what is the effect on the rate of nonsynonymous and synonymous subs if the amino acid is under purifying selection?

Answer 12

the rate of synonymous substitutions can be much higher than nonsynonymous

Question 13

what are the 3 mechanisms of gene duplication?

Answer 13

regions of chromosomes duplicated
whole genome doubled in polyploid organisms
DNA copies of mRNA in a cell can be inserted into the genome

Question 14

what are the 4 possible fates of gene duplicates?

Answer 14

both copies share original function
one copy decays through mutations (pseudogene)
copies differentiate in expression (same function but the 2 are regulated in dif ways/expressed at dif times
one copy acquires a whole new function (regulation and function differs - protein sequence changes)

Question 15

genes that control body axis orientation and segmentation during development are _____ (conserved or not conserved) across a diversity of organisms

Answer 15

conserved

Question 16

define hox genes

Answer 16

determine the “body plan” of an organism by observing segments in the body of an embryo

Question 17

define homeotic mutants

Answer 17

mutations with mis-regulated gene expression

ex. in drosophila - extra legs growing in place of antennae

Question 18

define genetic toolkit

Answer 18

regulatory genes that govern development processes that have been highly conserved throughout evolution

Question 19

define heterometry

Answer 19

shifts between species in the amount of gene expression that causes developmental change
ex. beak size of Darwin’s finches which depends on their diet

Question 20

define heterochrony

Answer 20

shifts in timing of the development process

ex. giraffes’ necks are longer because it has a longer growth period to allow vertebrae to grow correctly

Question 21

define heterotropy

Answer 21

altered spacial patterns of developmental genes

ex. apoptosis vs gremlin of chicks vs ducklings