Selection and Genetic Drift

Question 1

Genetic drift

Answer 1

allelic/random drift/Sewall Wright Effect
change in allele freq in pop due to random sampling
affects genetic comp of pop via sampling effect

Question 2

How does pop size affect genetic drift?

Answer 2

Increased size = decreased drift

Question 3

Importance of starting frequency

Answer 3

allelic freq will drift around the starting freq, deterministic—-stochastic

Question 4

Bottleneck

Answer 4

significantly enhanced drift
size reduced greatly for at least 1 gen
variation LOST

Question 5

Founder Effect

Answer 5

change in diversity following the founding of anew pop
sustained bottleneck (cumulative) enhances drift

Question 6

Affects of founder effect

Answer 6

increased freq of rare allelic cond
new pop has only a subset of original variance
gradual loss of diversity with every subsequent dispersal event

Question 7

Causes of inbreeding depression

Answer 7

• increased homozygosity= increased expression of deletarious alleles= lower fitness
• decreased heterozygosity= reduces fitness of inbred individuals at loci where balancing selection acts

Question 8

Inbreeding coeff F

Answer 8

F= (exp freq of heterozygotes- obs freq)/ exp freq

Question 9

Purifying selection

Answer 9

genotypes dont have = fitness
selection AGAINST genotype
reduction in fitness relative to other genotypes
carrier of bad allele- less fit- produce fewer offspring- incapable of reprod= allele lost
overall decrease in diversity

Question 10

Balancing selection

Answer 10

genotypes dont have =fitness
selection FOR genotype
Heterozygote advantage- het has greater fitness, “carriers” eg sickle cell anemia and malaria