Résumé
Because of its high mutation rate and maternal inheritance, mitochondrial DNA (mtDNA) has become one of the favorite tools of evolutionary and population biologists. It is a closed circular DNA molecule (16.5 kb long for mammals) carrying genes for 13 subunits of the respiratory chain complexes, 2 rRNAs and 22 tRNAs. Heteroplasmy associated with length variations of mtDNA has been described in a number of animal species including mammals. Insertion/deletions (Indels) of mtDNA generally occur in the noncoding region (D loop) surrounding the origin of replication and promoters of transcription and do not seem to affect the metabolic functions of mitochondria. However, deletions in coding regions of mtDNA have more recently been characterized in association with human mitochondrial myopathies and encephalomyopathies.