[Molecular genetics of phenylketonuria in Orientals--linkage disequilibrium between a termination mutation and haplotype 4 of the phenylalanine hydroxylase gene].

Phenylketonuria (PKU) is a common metabolic disorder among Chinese, with a prevalence of about 1 in 16,500 births. This frequency is very similar to that among Caucasians. Individual exons of the phenylalanine hydroxylase (PAH) gene with flanking introns were amplified by the polymerase chain reaction and cloned into M13 for sequence analysis. An Arg111-to-Ter111 mutation was identified in exon 3 of the PAH gene in a Chinese PKU patient. The mutation is in linkage disequilibrium with the mutant haplotype 4, most prevalent among Orientals. The mutation accounts for about 10% of Chinese PKU alleles and is not found in Caucasians, demonstrating that independent mutational events occurred in the PAH locus after racial divergence.