All of the following are characteristics of phenylketonuria except?

Question

a.)it is a single-gene disorder.

b.)it leads to a dietary requirement for tyrosine.

c.)it is treated by total elimination of dietary phenylalanine.

d.) it results in mental retardation unless treatment is started in infancy.

Answer 1

Actually there are two answers that are not correct.

b) is the answer you probably want. There is no dietary requirement for tyrosine even though the absent enzyme blocks the conversion of phenylalanine to tyrosine.

But Belle is also correct. Answer (c) is not characteristic. The goal of treatment is to restrict, but not entirely eliminate phenylalanine from the diet. As Belle stated, phenylalanine is an essential amino acid, and even people with PKU need it.

Answer 2

c.)it is treated by total elimination of dietary phenylalanine

This is the false answer. Restriction of phenylalanine is necessary, but some natural phenylalanine is essential in order to prevent deficiency of this essential amino acid.