Final answer:
Phenylketonuria (PKU) is a recessive genetic disorder caused by a deficiency in the enzyme phenylalanine hydroxylase, leading to toxic levels of phenylalanine if not properly managed with a diet low in phenylalanine.
Step-by-step explanation:
Understanding Phenylketonuria (PKU)
Phenylketonuria (PKU) is a genetic disorder in which individuals lack sufficient activity of the enzyme phenylalanine hydroxylase, leading to an inability to properly break down the amino acid phenylalanine into tyrosine. Inheriting phenylketonuria is a recessive trait, which means that both parents must carry at least one copy of the recessive allele for a child to potentially have the condition. If two heterozygous carriers have children, as depicted in the provided Punnett square (with 'N' representing the normal allele and 'p' representing the PKU allele), there is a 25% chance that any given child will express the PKU phenotype.
As PKU affects approximately 1 in every 15,000 births in the United States, it is crucial to diagnose and manage this condition early on. Newborns are routinely screened for PKU to start them on a modified diet low in phenylalanine, thereby avoiding the severe symptoms and neurological damage associated with high levels of this amino acid.