Over the past few years numerous whole genome linkage studies have been performed in which the inheritance of phenotypes and genetic markers is followed in families [12,40]. Two influential linkage scans, one in a Southwestern American Indian tribe, a population isolate [41], and the other in the large, predominantly Caucasian Collaborative Study on the Genetics of Alcoholism (COGA) dataset [42] found evidence for linkage of AUD near the chromosome 4 GABAA receptor subunit gene cluster. A subsequent COGA scan found strong linkage of resting EEG beta power, an intermediate phenotype for alcoholism, to the same chromosome 4 region [43]. This finding led to the discovery of the association of GABRA2 with AUD, a robust, widely replicated finding that will be discussed below.
