Enhanced induction by X-irradiation of DNA double-strand breakage in mitotic as compared with S-phase V79 cells

A marked enhancement of X-ray-induced DNA double-strand breakage was demonstrated for mitotic Chinese hamster (V79) cells compared with S-phase cells or asynchronous cultures, which can explain the high radiosensitivity of mitotic cells. However, mitotic cells required twice the level of DNA double-strand breakage to produce a lethal lesion of that required for S-phase or asynchronous cells, suggesting that repair in mitotic cells is less error prone.