Studies on preclinical models of phenylketonuria (PKU), an inherited metabolic disorder, have used two strains, BTBR and C57Bl/6, created via a chemically induced point mutation in the gene encoding the enzyme phenylalanine hydroxylase (BTBR<sup>enu2</sup> and C57<sup>enu2</sup>, respectively). This evidence concerns the gene PAH and phenylketonuria.