In a population that is in HardyWeinberg equilibrium for two

In a population that is in Hardy-Weinberg equilibrium for two alleles, D and d. D shows complete dominance over d (i.e. heterozygotes Dd have the same phenotype as homozygotes DD). 72% of the population shows the dominant trait. What proportion shows the recessive trait?

A) 72%

B) 26%

C) 28%

D) 36%

Solution

Ans. Given-

            I. Population is at HW equilibrium

            II. Alleles of the specified gene, D and d

            III. D shows complete dominance over d

            IV. Phenotype of DD and Dd genotypes are dominant and identical to each other.

            V. % of dominant phenotype (DD + Dd) = 72 %

Now,

Possible genotypes in the population = DD, Dd, dd , where DD + Dd are dominant trait, and dd is recessive trait.

That is, phenotype % (DD + Dd + dd) = 100%

Or, % dd = 100 % - % (DD + Dd) = 100% - 72 % = 28 %

Thus, % of recessive trait = 28%

Correct option- C. 28%