Quest 4: Chp 8

Question 1

Law of large numbers

Answer 1

actual frequencies mirror expected frequencies when sample sizes are very large

Question 2

Wright-Fisher Model

Answer 2

Allele frequencies in offspring differ from allele frequencies in the gamete pool due to the fact that gametes are selected at random - genetic drift

Question 3

Genetic drift

Answer 3

process of random fluctuation in allele frequencies due to sampling effects in finite populations

Question 4

Three consequences of genetic drift

Answer 4

1) all allele frequencies fluctuate over time
2) some alleles are fixed, others are lost, and fraction of heterozygotes decreases over time
3) separate populations diverge in their allele frequencies and which are present

Question 5

Population bottleneck

Answer 5

event that wipes out a portion of the population causing random allele loss

Question 6

Finding the probability an allele will become fixed due to genetic drift

Answer 6

equal to the allele frequency in that population

Question 7

leading edge expansion

Answer 7

reduced genetic diversity in a newly colonized area due to founder’s effect

Question 8

s

Answer 8

selection coefficient

Question 9

What does the selection coefficient (s) represent?

Answer 9

selection against an allele

Question 10

He

Answer 10

number of heterozygotes in a population

Question 11

Ne

Answer 11

effective population size

Question 12

Effective population size

Answer 12

population that is actively reproducing (contributing to the next generation)

Question 13

selectively neutral alleles can evolve, true or false?

Answer 13

true, via genetic drift

Question 14

Chance of fixation of an initial mutation

Answer 14

2s

Question 15

Rules of neutral theory of molecular evolution

Answer 15

When population size is large, selection determines allele frequency
When population size is small, drift determines allele frequency

Question 16

How to determine if selection or drift determines allele frequency

Answer 16

s > 1/2Ne, selection wins
s < 1/2Ne, drift wins

Question 17

2 claims of neutral theory of molecular evolution

Answer 17

1) most variation in a population is selectively neutral
2) most changes in the DNA are selectively neutral

Question 18

Subsitution

Answer 18

a nucleotide base that changes due to mutation and becomes fixed within the population

Question 19

mutations vs. subsituition

Answer 19

mutations are typically deleterious, substitutions are NEUTRAL fixed alleles

Question 20

Synonymous substitution

Answer 20

nucleotides in codon changes but codon encodes for same amino acid

Question 21

most common substituition

Answer 21

synonymous because it does not disrupt function

Question 22

Ka/Ks < 1

Answer 22

purifying selection

Question 23

Ka/Ks ~ 1

Answer 23

near neutrality

Question 24

Ka/Ks > 1

Answer 24

positive selection

Question 25

if an organism is experiencing positive selection, it is...

Answer 25

adapting to environment

Question 26

if an organism is experiencing purifying selection, it is

Answer 26

well adapted to its environment

Question 27

Founder's effect

Answer 27

genetic drift that occurs when a small group of individuals establishes a new population

Question 28

Pseudogene

Answer 28

genes that have lost their protein coding ability/function

Question 29

Molecular Clocks

Answer 29

observe rate of evolution in genes to determine how old a clade is

Question 30

genetic equidistant principle

Answer 30

if genetic changes are constant, members of a clade should be equidistant from the outgroup

Question 31

Two issues with molecular clocks

Answer 31

1) saturation becomes an issue as time passes 2) genes evolve at different rates

Question 32

genetic saturation

Answer 32

nucleotide mutates, but can mutate to its original identity

Question 33

When are molecular clocks most useful?

Answer 33

When comparing a single locus over a short period of time for closely related organisms

Question 34

Coalescent time

Answer 34

number of generations we must go back for a population to be reduced to 2 parental lineages; typically 2N generation

Question 35

In small populations coalescence occurs

Answer 35

recent

Question 36

In shrinking populations coalescence occurs

Answer 36

recent

Question 37

In a large population coalescence occurs

Answer 37

further back

Question 38

In a growing population coalescence occurs

Answer 38

further back

Question 39

How can coalescent time be used to determine when a mutation occured?

Answer 39

a mutation in set of gene copes at the same locus must have arose after the coalescent time of the set of genes