Among the 22 SNPs we genotyped, 8 SNPs had very low minor allele frequency (MAF), lower than 0.002. These SNPs were removed for analysis. Their respective locations and MAF are as follows: rs10225567 (Exon10, 0.00028), rs2302165 (Exon 9, 0.00029), rs769198 (Exon7, 0.00167), rs2234947 (Exon6, 0), rs17866780 (Exon2, 0.00084), rs769200 (Exon1, 0.00028), rs769202 (Exon1, 0), rs769194 (Exon1, 0). Pair-wise estimates of linkage disequilibrium (Abecasis and Cookson 2000) between the remaining 14 GRM8 SNPs in this study demonstrate that the SNPs showing the strongest association with the theta ERO as well as alcohol dependence phenotypes (Table 2) are in strong linkage disequilibrium with one another (detail data not shown). For example, the Lewontin’s standardized disequilibrium coefficients |D’| estimated for pairs from any two of the three SNPs that are significantly associated with both theta band ERO and alcohol dependence (Table 2), rs1361995, rs10487457, rs10487459, are all equal to 1.
