The common inbred mouse strains have been assigned to seven lineages based on detailed pedigree records and, more recently, extensive single nucleotide polymorphism comparisons (Petkov et al. 2004). Strains from the C57/C58 lineage are generally among the highest drinkers, while those related to the DBA lineage are low preferring (Wahlsten et al. 2006). Recently, it was fortuitously discovered by Yuri Blednov that an F1 hybrid between the C57BL/6J and FVB/NJ inbred strains drank even more ethanol than C57BL/6J mice in standard 2-bottle preference tests (Blednov et al. 2005). Other strains in the FVB (“Swiss”) lineage show wide variability in drinking—for example, RIIIs/J are above average drinkers, while BUB/BnJ are below average (Yoneyama et al. 2008). This result suggests a role for epistatic interactions between alleles common in the C57/C58 lineage and those common in the Swiss lineage. We are currently mapping QTLs responsible for the excessive drinking of mice that are heterozygous for the C57BL/6J and FVB/NJ alleles when compared to those that are homozygous for one or the other allele. To do this, the genome was searched for individual
