Evolution lecture 8

Question 1

haplotype

Answer 1

the multi-locus genotype of a chromosome or gamete

Question 2

Linkage equilibrium:

Answer 2

two loci are in linkage equilibrium when the genotype of a chromosome at one locus is independent of its genotype another locus.

Question 3

Linkage disequilibrium:

Answer 3

two loci are in linkage disequilibrium when there is a non-random association between a chromosome’s genotype at one locus and its genotype at another locus.

Question 4

populations can have identical ________ frequencies but different _______ frequencies in LD.

Answer 4

allele; chromosome

Question 5

Coefficient of LD

Answer 5

D = gABgab – gAbgaB, 0 for LE and ranges from -0.25 to +0.25

Question 6

A population in ________ ________ will not change chromosome frequencies from one generation to the next.

Answer 6

LE

Question 7

What are the three conditions for LE?

Answer 7

1. The frequency of B on chromosomes carrying the A allele is equal to the frequency of B on chromosomes carrying the “a” allele.
2. The frequency of any chromosome haplotype can be calculated by multiplying the frequencies of the constituent alleles.
3. The quantity D, the coefficient of linkage disequilibrium, is equal to zero.

Question 8

What creates LD in a population?

Answer 8

1 - selection
2 - genetic drift
3 - population admixture

Question 9

population admixture

Answer 9

o where two populations that do not have gene flow between them come together. Wind up with unreal representation

Question 10

when loci are in LD, selection at one locus can change allele frequencies at the ______.

Answer 10

other

Question 11

How do you get rid of linkage??

Answer 11

Recombination

Question 12

What is the recombination rate?

Answer 12

R, related to D. R = 0.5 when on separate chromosomes

Question 13

If genes are _____ each other on the same chromosome, it takes _____ to remove LD

Answer 13

1 - near

2 - longer

Question 14

red queen hypothesis

Answer 14

arms race, keep running as hard as you can to just stay in place. Need to evolve better defenses to evade pathogen attack and, pathogen needs to develop ways to get around the defenses.

Question 15

The persistence of sex is a ______, because a simple model shows that ______ females should rapidly take over any population.

Answer 15

1 - paradox

2 - asexual

Question 16

• Null model for a population in which females reproduce sexually and asexually, one each to start has two assumptions. What are they?

Answer 16

1. A female’s reproductive mode does not affect how many offspring she makes
2. A female’s reproductive move does not affect the probability that her offspring will survive

Question 17

How can assumption 1 be violated?

Answer 17

Assumption 1 is violated in populations where the male provides resources and parental care

Question 18

How can assumption 2 be violated?

Answer 18

Assumption 2 is violated in populations in which the male provides better genes

Question 19

Outcrossing rate:

Answer 19

the fraction of offspring fathered by males.

Question 20

Genetic load:

Answer 20

burden imposed by accumulating mutations in asexual species.

Question 21

Muller’s ratchet:

Answer 21

the loss of a group by drift is much easier than its re-creation by back mutations.

Question 22

____ breaks Muller’s ratchet.

Answer 22

sex

Question 23

Sex may be advantageous because it re-creates favourable _________ genotypes that have been lost to drift.

Answer 23

multi-locus

Question 24

When does muller’s ratchet move fastest?

Answer 24

small populations with mildly deleterious alleles

Question 25

Selection, on a trait of any sort, seems to favour ______.

Answer 25

recombination

Question 26

Once optimal genotypes arise, sex is disadvantageous. Why?

Answer 26

This is because segregation and recombination break up the advantageous genotypes they recently helped to create

Question 27

Sex reduces ____ by re-creating missing genotypes.

Answer 27

LD

Question 28

Sex is beneficial in populations subject to ________ selection.

Answer 28

directional