Nucleic acid synthesis during and after mitosis in the slime mold, Physarum polycephalum

Abstract

During metaphase and anaphase in the plasmodium of Physarum polycephalum, incorporation of radioactivity into nuclear RNA cannot be demonstrated by autoradiography after 5 min incubations in 3H-uridine at high concentration. However, a low but still discernible level of labeling is seen over nuclei after 10 min incubations starting during mitosis. It is concluded that the rate of RNA synthesis in the nuclei declines to a level not detected by autoradiography for a period of about 5 min but less than 10 min during mitosis. Nuclear DNA and RNA synthesis are shown to start together within 5 min immediately after anaphase; thus a G1 period between anaphase and the start of nuclear DNA synthesis is not demonstrable autoradiographically in the plasmodium of Physarum polycephalum.