Phylogenetic tree from sequence data at Skts5. Phylogenetic tree generated by parsimony analysis of four M. Spretus and two Swiss-derived M. musculus strains. DNAPars program from Phylip 3.66 was used to generate a parsimony tree from 40.1 kb of sequence data from mouse chromosome 12 derived from six of the seven mouse strains. Because no sequence differences existed between FVB/NT and NIH/Ola these mice were grouped on the tree. The four M. spretus strains cluster together. The STF/PAS mice show the greatest divergence within M. spretus.