The ADH region of the genome (Figure 3) arose from repeated gene duplication, and many genetic variations in this region are in high linkage disequilibrium (LD), i.e. are inherited together. There are many and often large ethnic differences in allele frequencies and LD patterns. For example, out of 110 SNPs analyzed in a set of European-American and African-American families, 88 had minor allele frequencies (MAF) that differed between the two groups by more than 0.05 (Edenberg et al., 2006) (Table 2). These factors complicate interpretation of the genetic association data and emphasize that it is important to separately analyze different populations and combine data only at the meta-analysis stage.
