Question

Phenyketonuria is an inborn error of metabolism caused by an autosomal recessive gene. The frequency of this allele in the population is 0.03. Assuming Hardy-Weinberg equilibrium, what is the expected incidence of phenyketonuria among the offspring of all matings in which both parents are found to be carriers?

A. 0.0009
B. 0.03
C. 0.25
D. 0.5

Answer 1

The expected incidence of phenylketonuria among the offspring of all matings where both parents are carriers is 25%, or option C, based on Hardy-Weinberg equilibrium and the autosomal recessive pattern of inheritance.

Step-by-step explanation:

Phenylketonuria (PKU) is an inborn error of metabolism caused by a deficiency of the enzyme phenylalanine hydroxylase, which is necessary for converting phenylalanine to tyrosine. In populations in Hardy-Weinberg equilibrium, the frequency of an autosomal recessive allele (q) is 0.03, and the incidence of the disease among offspring from matings where both parents are carriers (heterozygous) is 25%.

This is based on the Punnett square where the genotype 'p' represents the normal allele and 'q' represents the recessive allele associated with PKU. The phenotypes of the possible offspring would be 25% normal (NN), 50% carriers (Np), and 25% affected by PKU (pp).