Differences in the sequences of the genes that code for these enzymes are called polymorphisms, and these polymorphisms show ethnic diversity. One of the best understood polymorphisms of alcohol-metabolizing enzymes involves the gene that encodes the enzyme ALDH2. One allele of the ALDH2 gene, ALDH2*2, codes for a virtually inactive form of the enzyme. People carrying this allele experience alcohol-induced flushing, show an increased level of response to alcohol, and have lower rates of alcohol use and alcoholism compared with people without this allele (Wall et al. 1992). The ALDH2*2 allele is found in a large proportion (about 40 percent) of people of Far East Asian descent but is uncommon in people of other ethnicities.
