What is the gene product for phenylketonuria (PKU)?

• A. Beta Globin
• B. Phenylalanine hydroxylase
• C. Cystic fibrosis transmembrane conductance regulator
• D. Tyrosinase

Answer: (B)

Phenylketonuria (PKU) is a genetic disorder caused by a deficiency in the enzyme phenylalanine hydroxylase. This enzyme is crucial in the metabolic pathway that converts the amino acid phenylalanine into another amino acid, tyrosine. When phenylalanine hydroxylase is deficient or nonfunctional, phenylalanine accumulates in the body, leading to various neurological issues and developmental delays if not managed through dietary restrictions.

The gene that encodes phenylalanine hydroxylase is located on chromosome 12, and mutations in this gene lead to the characteristic symptoms associated with PKU. Therefore, the presence of functioning phenylalanine hydroxylase is essential for proper phenylalanine metabolism, making it the correct answer in this context.

The other options refer to different proteins or gene products associated with other conditions: beta globin is related to sickle cell disease, the cystic fibrosis transmembrane conductance regulator is linked to cystic fibrosis, and tyrosinase is involved in melanin production and is associated with albinism and other pigmentation disorders. These choices, while important in their respective contexts, do not pertain to the enzymatic malfunction seen in phenylketon