Most mouse studies of alcohol preference have used two mouse strains called C57BL/6 (B6) and DBA/2 (D2) that differ greatly in their alcohol preference and, consequently, alcohol consumption. These two strains of mice are inbred, meaning that all animals from that strain are genetically identical and that for each gene, the animals carry two identical alleles (i.e., are homozygous). The consistent difference between the two strains in alcohol preference suggests that these strains carry different alleles at many of the genes influencing alcohol-drinking patterns. These genes are often called quantitative trait loci (QTLs).
