Maternal inheritance of mitochondrial DNA during backcrossing of two species of mice.

As judged by restriction analysis, mitochondrial DNA shows strictly maternal inheritance during 6-8 generations of backcrossing in both directions between Mus domesticus and Mus spretus. The average number of paternal mitochondrial genomes contributed to the next generation is estimated to be no more than one per thousand maternal mitochondrial genomes contributed. Despite the estimated accumulation of over 2000 mutational differences between M. spretus and M. domesticus mtDNAs since their divergence from a common ancestor, each of these mitochondrial DNAs, whether on a M. spretus or a M. domesticus nuclear background, allows mice to develop with seemingly normal viability and fertility.