Relative durations of the cell cycle phases of Xenopus cells at different temperatures

It has been proved that the duration of each phase in cell cycle of Xenopus cells can easily be determined by counting cells in G1, S, G2 and M in autoradiographed and stained preparations, and multiplying the fraction of cell number in each phase with generation time (Tg). At some different incubation temperatures, the following results were obtained: (1) at 18°C, G1, S, G2 and M were 30.2h, 29.5h, 10.1h and 2.2h with the total generation time of 72h; (2) at 23°C, G1, S, G2 and M were 15.1h, 16.2, 4.3h and 0.4h with the total generation time of 36h; and (3) at 28°C, G1, S, G2 and M were 12h, 13.8h, 3.9h and 0.3h with the total generation time of 30h.