One of the receptors through which acetylcholine acts is encoded by a gene called CHRM2. In the COGA sample, linkage was observed between a region on chromosome 7 that contains the CHRM2 gene and alcohol dependence, and subsequent experiments confirmed that an association existed between alcohol dependence and the CHRM2 gene (Wang et al. 2004). This evidence concerns the gene CHRM2 and alcohol dependence.