Typing of families with classical phenylketonuria using three alleles of the Hindiii linked restriction fragment polymorphism, detectable with a phenylalanine hydroxylase cDNA probe. Family typing for PKU by linked HindIII RFLP.

A human phenylalanine hydroxylase cDNA clone was isolated from a human liver cDNA library. The size of the cDNA insert is approximately 2.4 kb and appears to be a near full length copy of a phenylalanine hydroxylase mRNA. This cDNA was used to probe for HindIII restriction enzyme polymorphisms in heterozygote typing of families with phenylketonuria. The use of three alleles of this polymorphism, as opposed to the two alleles as previously described, increases the informativity for typing - and therefore also for prenatal diagnosis - in certain families from 75% to 100%.