Heteroplasmy in mice with deletion of a large coding region of mitochondrial DNA

Polymorphism of animal mitochondrial DNA (mtDNA) has been shown to involvepoint mutations and limited length variations affecting essentiallynoncoding regions. In two wild mice of the European subspecies Mus musmusculus we found a mitochondrial mutant with a very large deletion in acoding region. The deletion is 5 kbp long (31% of the mitochondrialchromosome) and encompasses six tRNA genes and seven protein genes. The twomice were heteroplasmic: they contained a mixture of normal mtDNA and thedeletion mutant. Although the latter is functionally defective, itrepresents 78%-79% of the mtDNA molecules in our preparations from eachanimal.