A gene exists in two alleles, B and b. The frequency of B is 0.7. If a population is in Hardy-Weinberg equilibrium, what percentage of individuals would be Bb?

Answer 1

Hi Janis,

So, to solve this, you have to use two different formulas:

The first is the one for allelic frequencies:

p + q = 1

with p being the frequency of the dominant allele (for your question we’ll have this be for B) and q being the frequency of the recessive allele (for your question we’ll have this be for b).

If the frequency of B is 0.7, then plugging it into the equation we get:

0.7 + q =1

q= 1 – 0.7

q= 0.3

So, the two frequencies are B = 0.7 and b = 0.3

The second equation we need here is the one for genotype frequencies which is:

p2 + 2pq + q2 = 1

with p2 being the BB individuals

2pq being the Bb individuals

q2 being the bb individuals

Here you can just solve for 2pq, and that would be:

2(0.7)(0.3) = 0.42 or 42%

Please let me know if you have any follow up questions.

Stay healthy!

-Tim