The times at which cells irradiated with 9 The times at which cells irradiated with 9.5 Gy completed their first, second, third, and so on divisions after irradiation. The times at which cells irradiated with 9.5 Gy completed their first, second, third, and so on divisions after irradiation. A, REC:myc cells, all of which were nonclonogenic. B, REC:ras cells; •, the progeny of a cell that was clonogenic; ▵, the progeny of cells that were nonclonogenic. C, mean generation times for both the unirradiated REC:myc and REC:ras cells (9.5 Gy) are shown for the generation before the cells were irradiated (generation −1), the generation in which irradiation occurred (generation 0), and the following 1–6 generations. None of the irradiated REC:myc cells survived beyond generation 2. Unirradiated REC:ras cells located in a shielded area of the irradiated flask were also followed, and the mean generation times for these cells are also presented. Bars, SE. Helen B. Forrester et al. Cancer Res 1999;59:931-939 ©1999 by American Association for Cancer Research