Linkage disequilibrium at the human dopamine D2 receptor locus (DRD2) in three populations from Taiwan

There are now at least several polymorphisms distributed across the coding regions of DRD2. The TaqI A and B systems are roughly 30 kb apart; the TaqI A system is about 10 kb downstream from the last exon and the TaqI B system is about 5 kb upstream of exon 2 (which contains the initiation codon). Previous studies in U.S. Blacks and Caucasians have show significant linkage disequilibrium. We have studied three ethnic groups living on Taiwan: Chinese Han (44 individuals), Atayal (41 individuals) and Ami (40 individuals). All three groups show significant linkage disequilibrium between the TaqI A and TaqI B systems. The haplotype frequencies differ significantly among the three groups, Blacks and Caucasians; the magnitude of disequilibrium also differs among the six. However, all six groups show a pattern of higher than expected frequencies of A1B1 and A2B2, and lower than expected frequencies of A1B2 and A2B1.