A human autosomal recessive trait appears in 1 in 100 births.What percent of people are homozygous dominant for this trait?
A)0)01
B)0)10
C)0)18
D)0)81
E)0)90

Question

Quizplus · Accepted Answer

Since the trait is autosomal recessive, the only way for someone to be homozygous dominant is if both parents are also homozygous dominant. Since the trait appears in 1 in 100 births, the frequency of the homozygous dominant genotype would be much lower. The frequency of the homozygous recessive genotype (affected individuals) is q2 = 0.01, so q (the frequency of the recessive allele) is sqrt(0.01) = 0.1.

Using the equation p + q = 1, where p is the frequency of the dominant allele:

p + 0.1 = 1

p = 0.9

Therefore, the frequency of the homozygous dominant genotype (p2) would be:

p2 = (0.9)2 = 0.81 or 81%

A Human Autosomal Recessive Trait Appears in 1 in 100