genetic variance in in vivo metabolism (18, 94). In vivo studies in Europeans demonstrated that variants in ADH7 are associated with the early stages of alcohol metabolism, with additional effects in ADH1A, ADH1B, and ADH4 (18). Postabsorptive alcohol metabolism is affected by variants in the ADH7-ADH1C-ADH1B gene cluster. Approximately 20% of the total genetic variance for alcohol metabolism was attributed to the combined effects of variants in the ADH gene region (18). Because patterns of linkage disequilibrium across this genomic region vary among different ethnic populations (36, 104) and the frequencies of functional variants differ from one population to another, the effects of functional variants may be population specific.
