If an individual changes his diet because it is discovered he has phenylketonuria (PKU), then one can conclude that although he had the __________ for PKU, it did not lead to the __________ of retardation.

Question

Quizplus · Accepted Answer

PKU is caused by a recessive gene, meaning an individual must inherit two copies of the gene (one from each parent) in order to develop the condition. This would result in a specific genotype. However, it is only when the condition leads to the phenotypic expression of retardation (via an inability to metabolize phenylalanine) that it becomes clinically relevant. Thus, changing the diet to prevent the phenotypic expression of PKU indicates that the individual had the genotype for PKU but not the phenotype of retardation.

If an Individual Changes His Diet Because It Is Discovered