What genetic inheritance pattern is associated with Phenylketonuria (PKU)?

Phenylketonuria (PKU) is associated with an autosomal recessive inheritance pattern. This means that an individual must inherit two copies of the mutated gene—one from each parent—to express the condition. The gene involved in PKU encodes an enzyme called phenylalanine hydroxylase, which is necessary for the metabolism of the amino acid phenylalanine. When this enzyme is deficient due to the mutations in the gene, phenylalanine accumulates in the body, leading to the neurological problems associated with the condition.

In autosomal recessive inheritance, both parents may be carriers of the mutated gene but do not exhibit symptoms of the disorder themselves if they have one normal copy of the gene. It is only when an offspring inherits the mutated gene from both carriers that they develop PKU. This pattern is typical of metabolic disorders like PKU, where the expression of the disease requires both alleles to be defective.

Understanding the inheritance pattern is crucial for counseling families about the risks of recurrence in future pregnancies, and for identifying carriers within the population.