BIOL 8430 Understanding Evolution

Subject: Biology / General Biology
BIOL 8430 Understanding Evolution Spring 2017 Homework 2 – Week 3 Lectures: Multi-locus Selection, Mutation and Gene Flow

1. The forward and reverse mutation rates at a certain locus in E. coli are
A to a
5 x 10-5
a to A
3 x 10-3
a. What are the expected allelic frequencies (p^ and q^) if no other processes are
b. If allele “a” is a deleterious recessive, will natural selection be able to easily eliminate it
from this E. coli population? Why or why not?

2. Consider the contribution of the following gene to running speed in Alaskan huskies. We
examine the following population of huskies and find:
A2A2 a. Average Speed
6.0 m/s
9.0 m/s
12.0 m/s Relative Frequency
0.49 Calculate the mean running speed in this population of huskies. b. Assume that no dominance effects are present and calculate the additive genetic
variance (VGA) in running speed for this population. c. If the phenotypic variance (VP) for running speed is 6.74 m/s, and you have a big
kennel where you can raise plenty of husky pups, will you be able to use artificial selection to
improve running speed in your population of huskies and potentially win the Iditarod? Why or
why not (defend your answer mathematically)? d. If you feed your husky pups a high protein and nutritional diet, will this have an
impact on their running speed? Why or why not?

3. A mainland population of 1000 blue iguanas have the neutral alleles A1 and A2 with
frequencies of A1 = 0.50 and A2 = 0.50. A new population of blue iguanas is founded on
Lizard Island with a population size of 10 males and 15 females. The neutral alleles A1 and
A2 are present in the population with frequencies of A1 = 0.30 and A2 = 0.70.
Migrants begin moving from the mainland to Lizard Island at a rate of 1 migrant per generation.
a. Calculate the change in frequency (?p) of the A1 allele after one generation of
b. What will the new frequency (p? )??of A1 be in the island population after one
generation of migration ?

4. In the paper by Lailvaux et al. 2014, “Trait compensation and sex-specific aging of
performance in male and female professional basketball players,” based upon the
results shown in Figure 2, which sex shows a potential trade-off in performance
allocation between the three scoring types? Compensation between scoring types
involves which types of shooting? How does aging change the strength and direction of
natural selection over an athlete’s lifetime? What’s the fitness payoff for a professional
athlete (Hint: it is not survive longer and make more babies! Think of LeBron James)?

5. Distinguish between directional, disruptive and stabilizing selection on multi-locus traits.
Include in your answer, 1) how does the mean and variance of the distribution change as
a result of an episode of each kind of selection; 2) at what phenotype(s) is mean fitness
highest in the population; 3) how is the maintenance of genetic variability influenced by
each of these types of multi-locus natural selection. Using graphs to illustrate your
answers is a very good idea here.

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