To identify as yet unknown genes involved in alcoholism and other disorders, investigators can search the entire genetic material (i.e., genome) by testing for linkage between polymorphic markers and the expression of the disorder or a related behavior. This means that, by studying families with several affected individuals, researchers analyze whether specific alleles of those markers are more commonly found in people with the disorder or behavior than in people without it. Using markers that are evenly spaced across all chromosomes, one can analyze the entire genome using this approach and thereby identify susceptibility genes with no, or only limited, prior knowledge about the mechanisms underlying the disease process.
