DNA was extracted from frozen whole blood samples using the Puregene Genomic DNA Purification Kit from QIAGEN (catalog #158489, Valencia, CA, USA) following the manufacturer’s instructions. Based on previous reports of association with alcohol-related phenotypes and on linkage disequilibrium in this region, one SNP in GABRG1 (rs1497577) and one SNP in GABRA2 (rs279858) (r2=0.18) were genotyped using iPLEX Gold assays designed with MassArray Assay Design Software (Sequenom, San Diego, CA). SNP information is shown in Table 1.
