Phenylketonuria (PKU) Is a Metabolic Disorder That Results in a Mental

Multiple Choice

Phenylketonuria (PKU) is a metabolic disorder that results in a mental handicap when phenylalanine is present in the diet. It was found that putting children with this genetic defect on a special diet prevented the effects of the disease. This is an example of:

A) correlation between genotype and environment.
B) variable norms of reaction.
C) genotype-by-environment interaction.
D) phenotypic variation due to genetic variation.
E) None of the answer options is correct.