MICRONUCLEAR RNA SYNTHESIS IN PARAMECIUM CAUDATUM

Abstract

In a generation time of 8 hr. in Paramecium caudatum, the bulk of DNA synthesis detected by thymidine-3H incorporation takes place in the latter part of the cell cycle. The micro-nuclear cycle includes a G1 of 3 hr followed by an S period of 3-3 1/2 hr. G2 and division occupies the remaining period of the cycle. Macro-nuclear RNA synthesis detected by 5[image]-uridine-3H incorporation is continuous throughout the cell cycle. Mlcronuclear RNA synthesis is restricted to the S period. Ribonuclease removes 80-90% of the incorporated label. Pulse-chase experiments showed that part of the RNA is conserved and released to the cytoplasm during the succeeding G1 period.