the regions encompassing the ADH1C–ADH1B and ADH4–ADH5 genes. Conversely, a site of frequent recombination occurs within the ADH7 gene, which means that variations near the start (i.e., in the 5′ portion) of that gene are nearly randomly associated with variations in the other ADH genes (Han et al. 2005; Edenberg et al. 2006). The strong LD over most of the ADH gene region means that the coding variations of those genes that have been most frequently studied are probably closely associated with regulatory variations, making it difficult to determine the exact contributions of individual variants—a fact that has not yet been widely appreciated.
