NEET BIOLOGY

Detailed explanation-1: -If both of a child’s parents are carriers, there is a 25% chance that each parent will pass on the normal PAH gene. In this case, the child will not have the disorder. Conversely, there also is a 25% chance that the carrier parents will both pass along the mutated gene, causing the child to have PKU.

Detailed explanation-2: -Even women with less severe forms of PKU may place their unborn children at risk by not following the PKU diet. Babies born to women with high phenylalanine levels don’t often inherit PKU . But a child can have serious problems if the level of phenylalanine is high in the mother’s blood during pregnancy.

Detailed explanation-3: -Classical PKU is an autosomal recessive disorder, caused by mutations in both alleles of the gene for phenylalanine hydroxylase (PAH), found on chromosome 12. In the body, phenylalanine hydroxylase converts the amino acid phenylalanine to tyrosine, another amino acid.

Detailed explanation-4: -A Punnett square for the mating of two PKU carriers is shown here. From the Punnett square, one can see that for each child there is a 3/4 probability that the child will be healthy and a 1/4 probability that the child will have PKU.