Hybrids formed by fusion of X- or gamma-irradiated and non-irradiated mouse cells.

Hybrid cells were obtained by fusion of irradiated and non-irradiated mouse cells of two different lines; they differed from the parent lines and from the hybrid cells of non-irradiated parents in their morphological, growth and karyological properties. The frequency of their occurrence was lower than in hybrids from non-irradiated cells, and unlike the irradiated cells of the parent line, these hybrid cells were capable of permanent proliferation in vitro. Chromosomes of the irradiated parent line were preferentially eliminated from the karyotype of the hybrids.