Genetical Theory

Question 1

mutation/selection balance equation

Answer 1

p̂ = μ/s

Question 2

what does p̂ = μ/s indicate

Answer 2

frequency of the allele at population equilibrium = mutation rate / selection coefficient

Question 3

origin of species was published in

Answer 3

1859

Question 4

Ronald Fisher

Answer 4

1930 - published a book showing how Mendelian genetics supported Darwinian theories

Question 5

relative fitness

Answer 5

w(x) = w(x) / w(reference)

Question 6

absolute fitness (w)

Answer 6

probability of surviving x expected # of offspring

Question 7

h

Answer 7

dominance coefficient - added to describe heterozygotes
ex. h=0.5; heterozygotes benefit 50% as much as homozygotes

Question 8

s - selection coefficient

Answer 8

(absolute fitness of the trait under study) - (absolute fitness of the reference trait)
aka
w(x) - w(ref)

Question 9

selective sweep

Answer 9

an allele is favored by natural selection until it sweeps through an entire population

Question 10

stronger selection results in

Answer 10

faster fixation

Question 11

Δp = change in allele frequency between generations

Answer 11

Δp = (s)(p)(1-p)
when s < 0.1

Question 12

Δp is faster when

Answer 12

s is higher - selection is stronger

Question 13

greater genetic variation _______ Δp

Answer 13

increases

Question 14

the shape of the genetic sweep depends on ______

Answer 14

the dominance of the mutation sweeping over other alleles

Question 15

is it probable that a new allele will spread to fixation?

Answer 15

no!

Question 16

purifying selection

Answer 16

the selective removal of deleterious mutations from the gene pool

Question 17

why do deleterious mutations stick around?

Answer 17

existing mutations take generations to evolve out, and mutations keep occurring

Question 18

higher allele frequency means higher or lower mutation rate

Answer 18

higher

Question 19

how does linkage disequilibrium affect genetic diversity?

Answer 19

decreases genetic diversity surrounding the adaptive locus

Question 20

heterozygosity

Answer 20

measure of genetic diversity based on hardy weinberg equation - heterozygotes are the 2pq part

Question 21

pleiotropy results in ________

Answer 21

fitness trade-offs
a gene variant can be adaptive for one function, neutral/deleterious for other functions

Question 22

epistasis

Answer 22

when the fitness of an allele depends on the other genes/genetic context around it

Question 23

balancing selection

Answer 23

multiple alleles in a single locus remain in a population, instead of one allele becoming fixed

Question 24

causes of balancing selection

Answer 24

overdominance/underdominance
frequency dependent selection
multiple niche polymorphisms

Question 25

overdominance

Answer 25

heterozygotes can have higher fitness in some cases, making it beneficial for individuals to keep both alleles at the locus

Question 26

sickle-cell anemia is an example of what?

Answer 26

overdominance causing balancing selection - heterozygote genotype of sickle cell anemia has the highest relative survival as it lends resistance to malaria

Question 27

predict equilibrium allele frequency of overdominance

Answer 27

p̂s = (1-w1)/(2-w1-w2)

Question 28

underdominance

Answer 28

heterozygote is the least fit option, and populations are driven towards homozygosity

Question 29

does underdominance cause balancing selection

Answer 29

no!

Question 30

negative frequency dependence

Answer 30

individuals of the rarer phenotype have greater fitness

Question 31

positive frequency dependence

Answer 31

individuals of the more common phenotype have greater fitness

Question 32

multiple niche polymorphisms

Answer 32

fitness of an allele sometimes depends on: the other alleles in its genome ecosystem, range, etc.

Question 33

example of a multiple niche polymorphism

Answer 33

an allele can be beneficial in winter and deleterious in summer, so both alleles will persist

Question 34

when genotype frequency is very high or very low,

Answer 34

the allele frequency in hardy-weinberg equilibrium vs in natural selection is very similar

Question 35

more genetic diversity causes differences in

Answer 35

allele frequency when compared between HWE and natural selection