NEET BIOLOGY

Detailed explanation-1: -A gene change (genetic mutation) causes PKU, which can be mild, moderate or severe. In a person with PKU, a change in the phenylalanine hydroxylase (PAH) gene causes a lack of or reduced amount of the enzyme that’s needed to process phenylalanine, an amino acid.

Detailed explanation-2: -Babies with PKU are missing an enzyme called phenylalanine hydroxylase. It is needed to break down the essential amino acid phenylalanine. Phenylalanine is found in foods that contain protein. Without the enzyme, levels of phenylalanine build up in the body.

Detailed explanation-3: -The PAH gene provides instructions for making an enzyme called phenylalanine hydroxylase. This enzyme is responsible for the first step in processing phenylalanine, which is a building block of proteins (an amino acid) obtained through the diet.

Detailed explanation-4: -If individuals with PAH deficiency do not get treatment, phenylalanine can accumulate to harmful levels, which can cause irreversible intellectual disability, seizures, developmental delay, and behavioral problems. PAH deficiency causes a spectrum of disorders ranging from severe to nearly asymptomatic.

Detailed explanation-5: -Classic phenylketonuria is caused by a complete or near-complete deficiency of phenylalanine hydroxylase activity and without dietary restriction of phenylalanine most children will develop profound and irreversible intellectual disability.