Evidence from mtDNA sequences that common laboratory strains of inbred mice are descended from a single female

Abstract

The rapid evolution¹ and maternal mode of inheritance² of mitochondrial DNA (mtDNA) make it a valuable marker for individuals related by descent from the same female³. We report here a study of wild and inbred mice which illustrates this point. We have examined mouse mtDNA from various locales in the Northern Hemisphere using restriction enzymes that cut the molecule at an average of 150 sites and find a high level of restriction-site polymorphism in wild mice but no variation among the ‘old’ inbred strains. This result is surprising because the nuclear genomes of these strains are known to differ greatly from one another⁴. The old inbred type of mtDNA occurs rarely in wild mice and differs from other types in the wild by an average of 100 nucleotide substitutions. In possible contradiction of published breeding records, these findings indicate that only one female lineage contributed to the formation of all the old inbred lines. In addition, our study of new inbred strains provides genetic markers that will be useful in mouse developmental and cell biology.