Genesis and Wanderings: Origins and Migrations in Asymmetrically Replicating Mitochondrial DNA

Mammalian mitochondria maintain a small circular genome that encodesRNA and polypeptides that are essential for the generation of ATP throughoxidative phosphorylation. The mechanism of replication of mammalianmitochondrial DNA (mtDNA) has recently been a topic of controversy. Newevidence has led to a modified strand-displacement model that reconciles muchof the current data. This revision stems from a new appreciation for alternativelight-strand origins. We consider here some of the potential mechanisms forlight-strand origin initiation. We also consider further the susceptibility of branchmigration within replicating mtDNA molecules. The existence of alternative lightstrandorigins and a propensity for branch migration in replicating mtDNAmolecules exposes a new array of possible configurations of mtDNA. Theassortment and assignment of these forms is relevant to the interpretation ofexperimental data and may also yield insight into the molecular basis ofreplication errors.