In 1959, inbred mouse strains first were shown to differ in their tendency to drink alcohol (McClearn and Rodgers 1959), and studies with inbred strains continue to this day. Each inbred strain possesses a random collection of genes (i.e., genotype), but all the animals within a strain are genetically identical. This reduction in the genetic variation among the animals studied could increase the power to identify genes contributing to alcohol-related traits.
