Figure 1.

DBA/2 breeding history. D2 is the oldest inbred strain and originated as part of breeding efforts by C. C. Little around 1930. Since then, numerous D2 substrains were created by separation and breeding by different vendors, leading to genetic drift. These nearly identical lines create a valuable genetic resource for studying the downstream effects of spontaneous and naturally occurring mutations. In this case, a deletion (yellow lightning bolt) in the Klrd1 gene occurred in the D2J substrain (red shading) between 1984 and 1989, leading to a loss of CD94 expression. Several substrains, including D2Rj, derived from the population at Jackson Laboratory before 1984 did not inherit the deletion. Information regarding substrain derivation dates was compiled from individual vendor Web sites.