Incorporation of [³H]Thymidine into Nuclear and Mitochondrial DNA in Synchronized Mammalian Cells.

Human liver cells (Chang) were synchronized by cold shock. The second generation was scanned with two-hour pulses of [³H]thymidine. The incorporation of [³H]thymidine into nuclear and mitochondrial DNA during each pulse was determined. Maximal incorporation into the nuclear DNA occurred during S-phase (6 hours long) and to smaller extend during and shortly after cytokinesis. The mitochondrial DNA was most highly labeled between S-phase and cytokinesis. The nuclear DNA's had a buoyant density in caesium chloride of 1.699 g/ml, whereas themitochondrial DNA banded at a density of 1.688 g/ml. [ABSTRACT FROM AUTHOR]