Phenylketonuria (PKU) is an inborn error of metabolism that is inherited in an autosomal
recessive manner. It arises from a deficiency of phenylalanine hydroxylase, which is
responsible for converting phenylalanine to tyrosine and thereby hastening its catabolism.
To produce mouse models for the study of PKU, male mice were mutagenized with
ethylnitrosourea and their progeny were screened for the elevated phenylalanine levels
characteristic of phenylalanine hydroxylase deficiency. Of three mutant alleles recovered …