Answer:
a. What is the frequency of heterozygotes? 50%, heterozygotes are the ones that have one of each alelle (B and b). They will have brown hair as a phenotype.
b. What is the frequency of homozygous dominant? 25%, homozygotes are the ones that have the same allele twice (BB). They will also have brown hair.
c. What is the frequency of the b allele? 75%, compound of 50% brown hair and 25% blond hair.
150 represents 75% of 200. To achieve this percentage, two heterozygotes have to be cross:
Bb × Bb
↓ ↓ ↓ ↓
BB Bb bB bb
Because brown hair is dominant, each pair of alleles that has a B will have brown hair as a phenotype.
The pair of alleles that has 2b is the only one that will have blond hair (in this case 25%).
