Studies on radioresistance with HeLa cells: radiosensitivity and chromosome constitution

compared with those of the unirradiated original strain of cells. The modal chromosome number of the radioresistant 5 kR line of HeLa cells was found to be 64, and that of the original HeLa strain to be 71. The 5 kR line of cells contained one or two abnormally long acrocentric chromosomes which were almost absent in the parent line. The radiosensitive line of cells from a clone that was obtained by a single cell culture of the original