[Analysis of RFLP haplotypes and point mutations at the phenylalanine hydroxylase (PAH) locus in PKU families from north China].

A study of DNA polymorphisms at the phenylalanine hydroxylase (PAH) locus was performed using 28 classical phenylketonuria (PKU) families from North China. In the families analyzed, haplotype 4 accounted for 77% of normal chromosomes and 79% of PKU gene bearing chromosomes. Two new haplotypes, haplotypes 49 and 50, were found. On the basis of haplotype analysis, only 37%-40% of PKU carriers in North China were heterozygous and therefore informative for linkage studies. Exon 3 (Arg111----stop) and exon 6 (Tyr204----Cys204) mutations of the PAH gene were studied using the polymerase chain reaction (PCR) and allele specific oligonucleotide probe hybridization in 42 PKU families from North China. These accounted for 3.6% and 9.5% of PKU mutations in North China, respectively.