Susceptibility of X-Ray-Arrested HeLa S3 Cells to Additional Arrest

HeLa S3 cells arrested in G2 by a conditioning dose of 650 rad of 220 kV X rays delivered in early G2, were subjected to a second dose 10 hr after the first. In contrast to the survival response, which changes from that characteristic of late S cells to that of M cells early during arrest, susceptibility to additional delay is retained until the end of the arrest period.