A child presents with congenital phenylketonuria. Which statement is true regarding this disease?

Phenylketonuria (PKU) is a metabolic disorder caused by a deficiency of the enzyme phenylalanine hydroxylase. This enzyme is crucial for the conversion of the amino acid phenylalanine into tyrosine. When there is not enough of this enzyme, phenylalanine accumulates in the body and can lead to serious neurological issues, including cognitive impairment and developmental delays if not managed through dietary restrictions.

The correct answer highlights this enzymatic deficiency, underscoring the biochemical basis of PKU. Early detection through newborn screening and dietary management is essential to prevent the severe consequences associated with increased levels of phenylalanine.

The other options describe aspects that are not specific to PKU. The concept of red blood cell nuclei being defective does not pertain to this disease, as PKU primarily relates to metabolic function rather than cellular structure. PKU is inherited in an autosomal recessive pattern, which means it affects both male and female offspring equally and is not X-linked. Additionally, the transmission of PKU does not occur through sex chromosomes, but rather through the inheritance of two copies of the gene responsible for the enzyme deficiency, one from each parent. Therefore, the statement about PKU being passed from