Analysis of the linkage of the Taq1A and Taq1B loci of the dopamine D2 receptor gene with schizophrenia in patients and their siblings.

The linkage of the polymorphous markers Taq1A and Taq1B of the DRD2 dopamine receptor gene, located in region 11q22-11q23 of chromosome 11, with schizophrenia was studied. The investigation involved 29 complete families containing concordant and discordant sibling pairs. Common alleles at locus Taq1A were found significantly more frequently in concordant pairs (p = 0.04), and there was a tendency to a higher frequency of transmission of the maternal allele as compared with the paternal allele (p = 0.06). No such relationships were seen in the case of the Taq1B locus. Neither locus showed any significant difference in the frequency of common alleles in discordant pairs or in the predominance of allele transmission from one of the parents. These data demonstrate a possible linkage with schizophrenia for the Taq1A marker but not for the Taq1B marker.