The congenic strain B6.D2-Unc79Lwt harboring the Lightweight mutation was produced by backcrossing an ∼1.4 Mb region of mutagenized D2 genome from chromosome 12 onto the C57BL/6J (B6) strain for >10 generations. A genetically uniform B6 background was confirmed by genotyping this strain with a panel of 555 informative SNPs [24]. To produce animals for behavioral testing, B6.D2-Unc79Lwt heterozygous males were backcrossed to C57BL/6J females, with the exception of determination of MAC (the Minimum Alveolar Concentration of anesthetic required to abolish a tail pinch response in 50% of animals) and one of the ethanol preference tests, where B6.D2-Unc79Lwt heterozygous males were backcrossed to DBA/2J females.
