Question

In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population? You must show your work to get credit.

Answer 1

The hardy weinberg equation for genotype is :-

p2 + 2pq + q2= 1

In this, q2 is the recessive genotype.

Assuming that the Purple is Dominant and White is recessive, we can say that Purple flowers are a sum of both p2 and 2pq frequency . (Heterozygous normally shows dominant phenotype)

So q2 relates to white flowering plants.

Now to find q value, we have to first find frequency. To find the frequency of a genotype, the formula is :-

Number of individuals of that genotype / Total number of individuals.

Here total is 64 + 36 = 100

Frequency of white genotype = 64/100 = 0.64

So q2 = 0.64

Then q will be :-

q2 = 64

q = √0.64 = 0.8

Value of q is thus 0.8