Question

1. A bird species is found on two neighboring islands where wing colour and patterning is under the control of a single bi-allelic locus.16% of the bird population on island 1 has red-spotted wings, a recessive trait. Only 5% of the bird population on island 2 has red-spotted wings. Following a mass-migration event, 20% of island 2's population is made up of individuals from island 1. Answer the following questions:

1. What are the frequencies of the recessive allele on islands 1 and 2 prior to the migration event?

2. What is the frequency of the recessive allele in the bird population on island 2 following migration?

3. What is the frequency of heterozygous individuals in the population on island 2 after migration?

Answer 1

A)

On island 1, 16% of birds have red spotted wings. Therefore the frequency of the recessive genotype q2 = 0.16

Therefore, on Island 1, q = 0.4

On island 2, q2 = 0.05

=> q = 0.224

B)

The recessive allele frequency can be calculated as follows:

q = q(immigrants) * M + q(residents) * (1-M)

Where M is the proportion of Immigrants after the migration. Here,

q = 0.4 * 0.2 + 0.224 * (1 - 0.2) = 0.08 + 0.224 * 0.8 = 0.08 + 0.1792 = 0.2592

C)

After migration, the frequency of the recessive allele, q = 0.2592

=> p = 1 - q = 1 - 0.2592 = 0.7408

Thus,

Frequency of Heterozygous individuals = 2pq = 2 * 0.7408 * 0.2592 = 0.384

Thus the frequency of heterozygous individuals after migration is 0.384