Nucleic acid content of HeLa S3 cells during the cell cycle: variations between cycles.

The process of continuous resynchronization with excess thymidine provides sufficient cell material for accurate chemical determination of DNA and RNA in HeLa S3 cells at hourly intervals during the cell cycle. Total DNA is constant during the non-S phase portion of the cell cycle but varies widely among cycles of synchronous growth. Total cellular RNA content increases linearly in the G1 phase and accelerates to a higher linear rate of accumulation, which remains constant during most of the S and G2 phases. The ratios of early and late cycle rates of RNA accumulation are not constant among cycles.