Cell Cycle of Mouse Embryonic Tissue under Continuous Gamma-irradiation

THE cell cycle in proliferating mammalian tissues in adult animals commonly takes from 10 to 20 h. The DNA synthetic period ( S ) is fairly constant between 5 and 9 h and the post-DNA synthetic period ( G 2 ) is usually 1–2 h in duration. Most of the variability comes during the pre-DNA synthetic period ( G 1 ), although exceptions to this rule are known 1 . Among the shortest cycle times yet reported are those found in the normal and resected rat gut (8.2–9.4 h) (ref. 2), in the chronically irradiated mouse gut (∼8 h) (refs. 3 and 4) and in the neural tube of mouse embryos at 10 days gestation (probably ∼ 6.5 h; ref. 5).