Synthesis of mitochondrial DNA in vitro: Two classes of nascent DNAs

Abstract

1. In vitro synthesis of mitochondrial DNA was studied with isolated newborn rat liver mitochondria. The over-all synthesis of nascent DNA was about one-order higher than that of other systems previously reported. 2. The majority of the nascent DNA was initially observed in the closed circles and subsequently in both open and closed circles. 3. Two classes of the nascent DNA were obtained during the incubation: one class was the heat-dissociable fragments, and the other was alkali-dissociable higher-molecular DNAs. 4. The nascent DNA was found in both light and heavy bands in the alkaline CsCl gradient. 5. A plausible scheme is discussed in which replication of the circular mtDNA in vitro may be modulated by at least two steps: one related to discontinuity; the other operative for the semiconservative mode.