WEST-E Special Education Practice Test

Which condition is a metabolic genetic disorder characterized by the inability to convert phenylalanine into tyrosine?

1. Mitochondrial Disorder

2. Phenylketonuria (PKU)

3. Cystic Fibrosis

4. Galactosemia

The correct answer is: Phenylketonuria (PKU)

The correct answer is the condition known as Phenylketonuria (PKU). PKU is a metabolic genetic disorder that arises due to a deficiency in the enzyme phenylalanine hydroxylase, which is essential for converting the amino acid phenylalanine into another amino acid, tyrosine. When this conversion does not occur properly, phenylalanine accumulates to toxic levels in the body, potentially leading to serious health problems, including intellectual disabilities and other neurological issues if not managed through dietary restriction. Individuals diagnosed with PKU must adhere to a special diet that limits phenylalanine intake to prevent these adverse effects. This prevention method highlights the importance of understanding metabolic pathways and the consequences of enzyme deficiencies in genetic disorders. In contrast to the other conditions listed, mitochondrial disorders primarily affect energy production within cells; cystic fibrosis is a serious genetic disorder affecting the respiratory and digestive systems due to a malfunction in the CFTR gene; galactosemia, while also a metabolic disorder affecting the metabolism of galactose, is unrelated to the processing of phenylalanine. This distinguishes PKU as the unique disorder characterized specifically by the inability to convert phenylalanine into tyrosine.