Mouse family tree. The seven mouse groups as described as by Petkov et al.  with the strains examined in this study circled in red. Group 1, Bagg albino derivatives; Group 2, Swiss mice; Group 3, Japanese and New Zealand inbred strains; Group 4, C57/58 strains; Group 5, Castle's mice; Group 6, CC Little's DBA and related strains; Group 7, wild-derived strains. Modified from Petkov et al. and reprinted with permission . The length and angle of the branches were optimized for printing and do not reflect the actual evolutionary distances between strains.