COGA was designed as a family study, incorporating detailed assessments of the participants in many domains to allow derivation and study of endophenotypes along with diagnostic phenotypes. Genome surveys, using microsatellite markers, have been performed on both an initial dataset of 105 multigenerational pedigrees and a replication dataset with 157 multigenerational pedigrees. The results of genome surveys on these datasets have been published [e.g., [2-6]], along with analyses that combined the two [e.g., [7-12]]. Linkage studies of clinical phenotypes and electrophysiological endophenotypes have led to identification of genes involved in brain function as well as genes involved in alcohol dependence and related disorders. COGA has moved beyond identifying regions of linkage and is now identifying individual genes within those regions, using targeted single-nucleotide polymorphism (SNP) genotyping in which multiple SNPs were analyzed for each regional candidate gene. Genes identified include GABRA2 [9], GABRG3 [12], and CHRM2 [10,11].
