Maintenance of Genetic Variation I

Question 1

Define balancing selection.

Answer 1

Any form of selection, on its own or in conjunction with another evolutionary mechanism that maintains genetic variation within a population.

Question 2

What are the four types of balancing selection?

Answer 2

o Mutation selection balance
o Negative frequency dependent selection
o Heterozygote advantage
o Genotype x environment interactions

Question 3

Under which three conditions does mutation-selection balance increase?

Answer 3

o The strength of selection against a deleterious allele decreases
o The mutation rate increases
o When deleterious alleles are recessive

Question 4

When is mutation-selection balance thought to be particularly important?

Answer 4

for the maintenance of quantitative genetic variation, where the effective mutation rate is higher because many genes influence each trait

Question 5

What does this equation represent? Define all variables.

Answer 5

Calculating equilibrium frequency for recessive alleles under mutation-selection balance.
For an allele whose relative fitness is 1-s
mew = mutation rate
Solve for s using equation: relative fitness = 1-s

Question 6

What does this equation represent?

Answer 6

Equilibrium frequency of a dominant lethal allele under mutation selection balance

Question 7

Define frequency-dependent selection.

Answer 7

• An individual’s fitness depends on the frequency of its genotype/phenotype in the population

Question 8

What are the two types of frequency-dependent selection?

Answer 8

Positive and negative

Question 9

Define positive frequency-dependent selection

Answer 9

o Common genotype/phenotypes have the highest relative fitness

Question 10

Define negative frequency-dependent selection.

Answer 10

o Rare genotypes/phenotypes have the highest relative fitness