Population frequencies of the A1 allele at the dopamine D2 receptor locus.

The reported association of a polymorphic allele at the dopamine D2 receptor locus (DRD2) and alcoholism has recently been the focus of considerable interest and controversy. Evidence both for and against an association of the A1 allele of the TaqI A system have been reported. One of the inconsistencies in these studies is the frequency of the A1 allele in the controls. We undertook this study to determine the frequencies of the DRD2 A1 allele in different populations. The frequency of the DRD2 A1 allele was studied in 381 unrelated people from 16 different populations. On a global scale the frequency of the A1 allele was found to be dramatically different among the populations studied, from as low as 0.09 to as high as 0.75. Because of these significant differences an association study with this polymorphism must carefully control for ethnic origin of subjects and the results must be evaluated with caution.