Question

Some people have the ability to taste a bitter chemical called phenylthiocarbamide (PTC). The ability to taste PTC is due to the presence of at least one dominant allele for the PTC taste gene. The incidence of nontasters in North America is approximately 45%. Assuming the population is in Hardy-Weinberg equilibrium, what percent of the North American population is homozygous dominant for the ability to taste PTC? Provide your answer as a number between 0 and 1 to the nearest hundredth.

Answer 1

The ability to taste PTC is due to the presence of at least one dominant allele for the PTC taste gene, so a nontaster genotype should be homozygous recessive(pp). If the frequency of pp is 45%, then frequency of p would be:
pp=0.45
p= √0.45
p=67%

p+P= 100%
P= 100%- p
P= 100%-67%= 33%

The number of North American population that has is homozygous dominant(PP) genotype would be:
P=33%
PP= 33%^2= 10.89% = 0.1089 = 0.11