DNA was purified from venous blood samples using the DNA Extractor WB Kit (Wako Pure Chemical Industries, Ltd., Osaka, Japan). ALDH2 genotyping was performed by a previously described polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) method (Harada and Zhang, 1993). A total of 7 SNPs from GABRA2 gene were selected according to the prior research (Lappalainen et al., 2005): rs567926, rs534459, rs529826, rs279869, rs279858, rs279837, and rs9291283. These SNPs were genotyped using the TaqMan method on an ABI GeneAmp PCR System 9700 apparatus (Applied Biosystems, Foster City, CA). The location of the 7 GABRA2 SNPs is presented in the previous study (Covault et al., 2004).
