Cell Cycle Dependence for the Induction of 6-thioguanine-resistant Mutations: G₂/M Stage is Distinctively Sensitive to ²⁵²Cf Neutrons but Not to ⁶⁰Co γ-rays

Summary

Cell cycle dependence for the induction of 6-thioguanine-resistant mutation was investigated using synchronized mouse L5178Y cells after exposure to 4 Gy to ⁶⁰Co γ-rays or 1 Gy of ²⁵²Cf radiation (fission neutrons). Maximal mutation frequency was observed immediately after release from colcemid block (G₂/M phase) after ²⁵²Cf radiation, whereas it was 1 h after the release (G₁ phase) after ⁶⁰Co γ-rays. When the mutation frequency was plotted against the surviving fraction, a general correlation was observed between the two parameters except for G₂/M and G₁ phases which were more mutable per lethal event for ²⁵²Cf and ⁶⁰Co radiations, respectively.