A botanist is investigating a population of plants whose pet

A botanist is investigating a population of plants whose petal color is controlled by a single gene whose two alleles are incompletely dominant. She finds 170 plants that are homozygous brown, 21 plants whose petals are purple-brown, 340 plants that are homozygous purple. Is this population in HWE? How do you know?

Solution

As per the given data,

The frequency of homozygous brown, BB (p²) in the population is = 170/531 = 0.32

The frequency of heterozygous, purple-brown Bb (2pq) in the population is = 21/531 = 0.039

The frequency of homozygous purple (q²) in the population is = 340/531 = 0.64

ALLELE FREQUENCIES:

Freq of brown = frequency of p = p² + 1/2 (2pq) = 0.32 + 1/2 (0.039) = 0.32 + 0.0195 = 0.3395

Freq of purple = frequency of q = q² + 1/2 (2pq) = 0.64 + ½ (0.039) = 0.64 + 0.0195 = 0.6595

The frequency of p + q = 0.3395 + 0.6595 = 1

Thus, the population is in H-W equilibrium.