Figure 1. The breeding strategy for creating the BXD recombinant inbred strains is shown. The parental strains were C57BL/6J female mice and DBA/2J male mice. The mice were bred to produce an F1 cross, and the F1 mice were bred again to produce an F2 generation. The mice were inbred through brother-sister mating for at least 20 generations to produce inbred sub-strain populations. Currently, 150 BXD strains are available.