The reference allele of the ADH1C gene is ADH1C*1, with an arginine at position 272 (Arg272) and an isoleucine at position 350 (Ile350). The ADH1C*2 allele, with a glutamine at position 272 (Gln272) and a valine at position 350 (Val350), is common in Europeans and African Americans. The ADH1C*3 allele, with a threonine at position 352 (Thr352), is found in Native Americans (33). Studies have shown that ADH1C*1 also has protective effects on the risk for alcohol dependence in people of Asian and African descent (33, 96). However, some studies showed that the protective effect of the ADH1C*1 allele is not an independent effect owing to the linkage disequilibrium of this allele with the ADH1B*2 allele (24, 103).
