Question

In a diploid population of Drosophila $9\%$ of the population is black in colour. Black is recessive to grey. What is the frequency of heterozygous flies in that population, if it is in Hardy-Weinberg equilibrium?

• A. $0.42$
• B. $0.09$
• C. $0.49$
• D. $0.70$

Answer 1

The correct option is A $0.42$

Let the recessive allele for black colour be represented by q and dominant by p

Thus, heterozygous allele will be pq

For a population of 100 Drosophila

Allelic frequency of q$2$ = 9÷100=0.09

q=0.3

From Hardy Weinberg law, (p+q)$2$=1

p+q=1

p=1-q=1-0.3=0.7

Also, p$2$ + q$2$ + 2pq =1

Putting the values,

(0.7)$2$ + (0.3)$2$ + 2pq =1

0.49 + 0.09 + 2pq= 1

0.58 + 2pq =1

2pq= 1-0.5=0.42

pq=0.42/2= 0.21

So, the correct option is '0.42',