Evolutionary relationships between laboratory mice and subspecies of Mus musculus based on the restriction fragment length variants of the chymotrypsin gene at the Prt-2 locus.

Restriction endonuclease fragment length variants in mice were compared by Southern blot analysis using the cDNA probe pcXP33 for the chymotrypsin gene. The variants were detected in the restriction patterns generated by fragments from digestions with BglII, EcoRI, HindIII, Pstl, SacI, and XbaI. The set of protein phenotypes and the restriction patterns of chymotrypsin gene were examined in many laboratory strains and wild subspecies. Most laboratory strains (26 strains) are grouped into a set defined as Set 1, but only a few laboratory strains (AU/SsJ and five BALB/c sublines) are classified as belonging to Set 2. Of wild subspecies, only BRV-MPL (M. brevirostris) can be placed in Set 1, while DOM-BLG and SK/Cam (M. domesticus) belong in Set 2. The assignment of an appropriate set defined by the characteristics of the chymotrypsin gene has also been investigated in M. musculus, two Chinese subspecies, M. yamashinai, M. molossinus, and M. castaneus, and the evolutionary relationship between laboratory mice and various subspecies of Mus has been examined.