Mutation & Migration Practice Problems

For a mutation to affect the allele frequency in a population over time where would the mutation have to occur? (assume no other evolutionary mechanism when answering this question)

In an individual’s germ line cells

White eyes in Drosophila were first observed in a lab population in January of 1910. If the forward mutation rate (e.g. red —> white) is 10-5 per bp/year and the backward mutation rate (e.g. white —> red) is 3 x 10-6 bp/year, what is the equilibrium frequency of the white allele?

1. Identify what is given: μ = 10^-5; v = 3x10^-6

2. Identify what is asked for: q̂

3. Select the appropriate equation: q̂ = μ/v + μ

4. Solve: q̂ = 10^-5/(3 ∗ 10^-6+ 10^-5) = 0.77

In the cave that’s completely dark, eyelessness (no eyes) is:

• Beneficial to the shrimp (increases fitness)

• Selectively neutral (no measurable impact on their fitness)

At the surface (not in the cave), eyelessness is:

Deleterious to the shrimp (reduces fitness)

The typical mutation rate for most genes is 2.5x10-8 bp/generation. If a locus has a strong selective pressure (e.g. s = 0.98), what will the equilibrium frequency of the recessive allele at the locus be?

1. Identify what is given: μ = 2.5x10^-8 bp/generation, s = 0.98

2. Identify what is asked for: equilibrium frequency (q̂)

3. Select the appropriate equation: q̂ = √μ/s

4. Solve: q̂ = √2.5x10^-8/0.98 = 1.6x10^-4

The Florida panther population consisted of 30 individuals, with a r allele frequency of 0.31. In contrast, the Texas cougar population had a population of 7000 with a r allele frequency of 0.08. If 8 individuals were moved from Texas to Florida, what would the new frequency of the r allele be in the Florida population?

• pc = 0.08

• pi = 0.31

• m = 8/38 = 0.21

• Δp = m(pc – pi) = 0.21(0.08 – 0.31) = -0.05

• pnew = 0.31 – 0.05 = 0.26

Some people living in Tibet carry an allele that allows them to tolerate the low oxygen conditions of the Himalayas better than individuals without this allele. Predict what would likely happen if a small family of Tibetans migrated to Chile where people must tolerate low oxygen conditions due to the Andes mountains

Overtime, the frequency of the Tibetan allele would decrease in Chile

What is the equilibrium frequency of the p allele with a forward mutation rate of 10^-6 bp/year and a backward mutation rate of 4 x 10^-7 bp/year?

A novel allele in human T-cells (T’) allows some individuals to be naturally resistant to. HIV infection developing into AIDS. If the forward mutation rate (T —> T’) for this gene is 5 x 10-9 per bp/yr, what will the new allele frequency for the original allele (T) be at equilibrium if the strength of selection is 0.03? Assume the new allele (T’) is recessive

The Florida panther population consisted of 38 individuals, with a deleterious r allele frequency of 0.24. In contrast, the Texas cougar population had a population of 7000 with a deleterious r allele frequency of 0.08. How many individuals from the Texas population would it take to decrease the r allele frequency in Florida panthers to 0.1?

The mutation rate for hemoglobin to sickle cell (Hg —> S) is 1.7 x 10^-8 bp/generation. The backward mutation rate (S —> Hg) is 1.1 x 10^-8 bp/generation.

a. If mutation were the only mechanism changing allele frequency of hemoglobin, what would the allele frequency of S be at equilibrium? Assume the current frequency of the S allele is 0.10.

b. What would the equilibrium frequency of the S allele be if the average strength of selection is 0.77?

Many reef fish have pelagic (that is, open water) larval forms that can be dispersed by currents to new reefs. If a population of 8080 dusky damselfish in Mozambique had an allele frequency of h = 0.69 and a population in Madagascar of 3200 dusky damselfish had an allele frequency of h = 0.47, what would the new allele frequency be in Madagascar if it received 100 Mozambique larvae?