Hardy-Weinberg Question-Please Help!

Question

A population of rabbits may be brown (the dominant phenotype) or white (the recessive phenotype). Brown rabbits have the genotype BB or Bb. White rabbits have the genotype bb. The frequency of the BB genotype is 0.75

What is the frequency of heterozygous rabbits?

What is the frequency of the B allele?

What is the frequency of the b allele?

Answer 1

The Hardy Weinberg formulas you would want to use to answer these questions:

(1) p + q = 1

p - frequency of dominant allele (in this case B)

q - frequency of recessive allele (in this case b)

(2) p²+2pq+q² = 1

p² - frequency of the homozygous dominant genotype (BB)

2pq - frequency of heterozygous genotype (Bb)

q² - frequency of recessive genotype (bb)

You are given that the frequency of the BB genotype is 0.75. Since p² is the frequency of the homozygous dominant genotype, this means that p² = 0.75. You can then solve for p.

What is the frequency of the B allele?

p is simply the frequency of the B allele, which you already solved for above.

What is the frequency of the b allele?

Use equation (1) to solve for q, which is the frequency of the b allele. You already have the value of p.

What is the frequency of heterozygous rabbits?

You should have values for p and q from the first two questions. Now plug these values into p² and q^{2 in} equation (2) and solve for 2pq. Alternatively, you can also plug values of p and q into 2pq directly. Both ways are equivalent.

This is the blueprint. Happy to walk through step by step -- please book some time with me on Instant Book!