A population of finches on an oceanic island varies at a particular gene locus. The current allele frequency is A 1 = 40%, A 2 = 60%, and there are 12,000 birds on the island. On the nearest continental mainland, the same species is monomorphic for allele A 1. If 3,000 birds migrate from the mainland to the island, by how much will the frequency of allele A 1 change on the island? Group of answer choices 0.15 0.12 0.08 0.45 0.48

The frequency of allele will change by 0.12 on the island

Explanation:

A certain allele's frequency is calculated as the total amount of individuals with that particular gene allele divided by the total population number.

Thus, if A1 frequency is 40% that means that, for the case that the population was 100 individuals, 40 individual would have that allele. In our case, the oceanic island shelters 12,000 finches, so one can calculate the total amount of finches with allele A1 as follows:

Total finches with A1 on the island = 0.4 x 12,000 = 4,800 finches with A1

Then, if 3,000 birds with allele A1 migrate from continent to the island they will be added to the 4,800 finches already living on there. Additionally, the population number will also be increased in 3,000 individuals.

In this new situation, the new A1 frequency is:

A1 frequency on the island after migration = (4,800 + 3,000) / (12,000 + 3,000) = 7,800 / 15,000 = 0.52

This means that the new A1 frequency on the island is 52%.

If we calculate the change in the frequency of allele A 1 on the island, we must subtract the previous frequency to the new one.

Numerically this means doing:

Change in the frequency of allele A 1 on the island = 0.52 - 0.4 = 0.12

Thus, the frequency has changed by 12%.