Question

1. You lead a research team that finds ​two non-migrating Southern Hemisphere populations​ of bunyips​ that are isolated from one another: one on a very cold island near Antarctica, and one on a tropical and very pleasant island near the equator.

Through observation and experiments, you realize that ​cold tolerance​ is controlled by a single locus you uncreatively call ​cold​, with ​three alleles: ​A, a,​ and ​X​. You also find out that ​A​ mutates into either ​a​ or ​X​ at an unknown rate. You discover bunyips are diploid, with two alleles per locus.

1. The mutation rates from ​A​ into ​a​ or ​X ​are ​unknown​. It appears that homozygotes for ​a and ​X​ are more fit in cold environments. One of your novice team members proposes that you should try to estimate these rates for both bunyip populations, and predicts that the mutation rates are faster in the population that lives on the cold island near Antarctic. Are they right? Why or why not?

2. You don’t know if mutation to ​a​ or to ​X​ has a larger effect on fitness. Someone accidentally transplants some of the tropical bunyips to the Antarctic island, creating a new population of bunyips. The ones still on their home island seem well-adapted to their warm climate with high fitness, while the ones that were accidentally moved seem extremely unhappy with low fitness. In which of these two populations is a mutation with a large effect more likely to be beneficial? Why?

3. You focus on one population of the bunyips, for now. You sample 100 of them and record their genotypes as follows. What are the frequencies of each of the three alleles?

genotype	AA	Aa	aa	AX	aX	XX
# of individuals	14	29	5	33	19	0

d. Calculate the Hardy-Weinberg equilibrium ​genotype​ frequencies for these three alleles, and ​fill it in the table below​. Please show your work below the table. To do this for three alleles, you’ll have to think through the logic for why these frequencies are ​p​^2​, ​2pq​, and q​^2​ for two alleles with frequencies ​p​ and ​q​. What are they for three alleles with frequencies ​p​, ​q​, and ​r​?

genotype	AA	Aa	aa	AX	aX	XX
HW frequency

Answer 1