CLONAL HETEROGENEITY IN THE PROGENY OF HELA-CELLS WHICH SURVIVE X-IRRADIATION

Clones of HeLa cells that had survived 9 Gy X-rays were investigated f or plating efficiency, radiosensitivity, the proportion of giant cells , and chromosome numbers. A significant decrease in plating efficiency was observed that persisted for >20 population doublings. The reduced plating efficiency was associated with an increased proportion of gia nt cells in the colonies. There was pronounced clonal heterogeneity in the progeny of irradiated surviving cells with respect to plating eff iciency, proportion of giant cells, and chromosome numbers. The radios ensitivity of progeny from irradiated cells did not change compared wi th controls.