Question

A butterfly species is found on two neighbouring islands. 8% of the population on island 1 has spotted wings, a recessive trait (the presence of wing spots is encoded by a single locus with two alleles). Only 5% of the population on island 2 has spotted wings.

Some butterflies from island 1 were blown to island 2 during a severe hurricane and 20% of island 2’s population now consists of individuals blown over from island 1. Answer the following questions:

Q1 What are the frequencies of the recessive allele on islands 1 and 2, respectively?

Q2 What is the frequency of the recessive allele in the butterfly population on island 2 after the hurricane?

Q3 What is the expected influence of such a migration on allele frequencies among populations?

Answer 1

1. In island 1 the frequency of the recessive gentopye = p²= 8/100 = 0.08

So the frequency of the recessive allele= p =p² = 0.08 = 0.28

In island 2 the frequency of recessive genotype= 5/100= 0.05

Frequency of the recessive allele = p= 0.05 = 0.22

2. Frequency of the recessive genotype after migration= 20/100= 0.2

Frequency of the recessive allele = 0.2 =0.44

3. Here the spotted wings butterfly are migrating into the population of island 2. Therefore, they are immigrating into the population and will cause gene flow. This would result in the increase in the frequency of the recessive allele in the population.