Phenylketonuria (PKU) is an inherited metabolic disorder caused by a recessive allele, hhh. The dominant allele, HHH, codes for the functional enzyme phenylalanine hydroxylase, which converts the amino acid phenylalanine into tyrosine. Without this enzyme, phenylalanine builds up to toxic levels in the body.
A mother who is a carrier (heterozygous) and a father who has PKU (homozygous recessive) wish to have children.
State the genotypes of both parents, list the possible genotypes of their children, and determine the probability (as a percentage) that a child will inherit phenylketonuria.
Suggest why individuals with phenylketonuria must adhere to a strict diet that is extremely low in protein.
Explain how the resulting accumulation of phenylalanine leads to reduced brain development and neurological damage in untreated individuals.
