A population of songbirds has migrated to a dense patch of forest that is heavil

ID: 167953 • Letter: A

Question

A population of songbirds has migrated to a dense patch of forest that is heavily dominated by pine. The birds show three possible feather coloration patterns. After observing 1000 birds, you observed 25% dark plumage, 65% mottled plumage, and 10% light plumage.

What is the frequency of the dominant allele D (dark plumage) and the recessive allele d (light plumage)?

Is this population in Hardy-Weinberg equilibrium (be sure to do a Chi Square to check).

What genotype is in excess in this population? What type of selection effect is being seen?

Explanation / Answer

Answer - Frequency of the dominant allele D (dark plumage) and the recessive allele d (light plumage):

As per given details, 25% of the 1000 birds, meaning 250 birds have dark plumage (DD), 65% or 650 have mottled plumage(Dd) and 10% or 100 have light plumage(dd). So, the constitution will be as below.

Genotype

# of Individuals

Genotypic frequencies

250

DD = 250/1000 = 25%

650

Dd = 650/1000 = 65%

100

dd = 100/1000 = 10%

Total

1000

The entire population consists of 2000 (1000 X 2) alleles. To determine the allelic frequencies, we simply count the number of dominant or recessive alleles and divide by the total number of alleles. So, the allelic frequency for the dominant D allele will be:

f(D) = [(2 x 250) + 650]/2000 = 0.575

and the frequency for the recessive d allele will be:

f(d) = [(2 x 100) + 650]/2000 = 0.425