RADIATION RESPONSE OF AN INTRASPECIFIC SOMATIC-CELL HYBRID (L5178Y, X-RAY RESISTANT LINE X L5178Y, X-RAY SENSITIVE LINE)

The radiosensitivities of an X-ray-sensitive L5178Y line, an X-ray-resistant L5178Y line, and of two hybrid lines produced by their fusion have been studied. The hybrid cells are similar in X-ray resistance to the more resistant parent. There was no significant difference in the extrapolation number of the survival curves nor in the ability of the parental and hybrid cells to recover from sublethal damage in dose-fractionation experiments. The radiosensitivities of tetraploid sublines of the two diploid parental lines were also studied and it was shown that the resistance of the hybrid cells is not related to the increase in chromosome number, interaction between the two genomes being ultimately responsible.