Question

The ability to taste the bitter compound phenylthiocarbamide (PTC) is anautosomal dominant trait. The inability to taste PTC is a recessive condition. In a sample of500 people, 360 have the ability to taste PTC and 140 do not. Calculate frequencies of: a) recessive allele, b) dominant allele, c) each genotype

Answer 1

Frequency of dominant allele (p) = 0.471

Frequency of the recessive allele (q) = 0.529

Frequency of homozygous recessive genotype (q^2)= 0.28

Frequency of homozygous dominant genotype (p^2) = 0.222

Frequency of heterozygous dominant genotype (2pq) = 0.498

Step-by-step explanation:

Out of 500 individuals, proportion of the homozygous recessive genotype (the people that can not taste PTC) = 140

Frequency of homozygous recessive genotype (q^2)= 140/500 = 0.28

Frequency of the recessive allele (q) = square root of 0.28 = 0.529

Since p+q = 1 (p = frequency of dominant allele and q = frequency of recessive allele)

Frequency of dominant allele (p) = 1-q = 1-0.529 = 0.471

Frequency of homozygous dominant genotype (p^2) = 0.471 x 0.471 = 0.222

Frequency of heterozygous dominant genotype (2pq) = 2 x 0. 471 x 0.529 = 0.498