5/6/24 - Lecture 19: Population Genetics IV: Maintenance of Variation

Question 1

Recessiveness

Answer 1

Effects of allele only seen in homozygotes

Question 2

Delayed onset of phenotypic effects

Answer 2

The effects of some alleles are not apparent until after reproduction

Question 3

Forms of balancing selection

Answer 3

Heterozygote advantage, antagonistic pleiotropy, fluctuating selection, negative frequency-dependent selection

Question 4

What does balancing selection do?

Answer 4

It acts to maintain allelic polymorphisms within populations

Question 5

Heterozygote advantage

Answer 5

Heterozygotes have higher fitness

Question 6

Antagonistic pleiotropy

Answer 6

When one allele gives both benefits and drawbacks (example of sickle cell allele)

Question 7

Fluctuating selection

Answer 7

Directional selection can change direction over time or space

Question 8

Negative frequency-dependent selection

Answer 8

Rare genotypes have higher fitness.

This might be due to preference for novelty (inbreeding avoidance, predator search image), resource exploitation, and disease resistance

Question 9

What does a negative frequency graph look like over time?

Answer 9

Fluctuating from lower to higher frequency.

This is because the rare phenotype is more fit, which then becomes more common

Question 10

Positive frequency-dependent selection

Answer 10

The common phenotype is more fit

Question 11

Allelic polymorphism

Answer 11

When more than one allele occupies a gene’s locus within a population