Question

(3) Some people can taste the bitter compound phenylthiocarbamide while others cannot. This trait is governed by a single autosomal gene; the allele for tasting is completely dominant with respect to the allele for nontasting. Among 1707 Hawaiians tested for the ability to taste, 1326 tasters were found. Assuming that the population is at Hardy-Weinberg equilibrium for this gene and that mating is purely random: a. What are the allele frequencies for the tasting allele T and for the nontasting allele t? b. What are the genotype frequencies in the population? C. Of all of the matings in the population, what proportion will be between two nontasters?

Answer 1

Total number of individuals = 1707

Number of tasters = 1326

Number of non tasters = 1707 - 1326 = 381

Tasters = TT, Tt

Non tasters = tt

Genotypic frequency of non tasters = tt = 381/1707 = 0.224

Allelic frequency of t = √0.224 = 0.473

Allelic frequency of T = 1 - 0.473 = 0.527

Genotypic frequency of TT = 0.527 × 0.527 = 0.278

Genotypic frequency of Tt = 2 × 0.527 × 0.473 = 0.498

Proportion of mating between two non tasters = tt × tt × 100 = 0.224 × 0.224 × 100 = 5.01%

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