Coat color in cats is partially determined by the Xlinked O

Coat color in cats is partially determined by the X-linked O locus. OO females and OY males are orange, while oo females and oY males are black. Oo females are a mosaic of orange and black (calico cats). In a population of cats at Hardy-Weinberg equilibrium, 20% of males are orange. What is the expected frequency of calico cats in this population?

Solution

The coat color in cats is determined by X-linked O locus. The following genotypes and phenotypes are observed.

According to Hardy- Weinberg equilibrium,

p² + 2pq + q² = 1 and also p+q =1In this question, the dominant alleles OO is given which is 20 %. So calculate O.

calculate p= 20%, which is 20/100 = 0.2

Now, we know p+q=1. So, 0.02+q = 1

So, q = 0.8

Now, The calico cats are heterozygous. So, the expected frequency of calico cats will be 2pq

2pq= 2X 0.2X 0.8= 0.32