Excessive chromosome fragility and abundance of sister-chromatid exchanges induced by UV in an Indian muntjac cell line defective in postreplication (daughter strand) repair.

Two UV-hypersensitive animal cell mutants defective in postreplication recovery (daughter strand synthesis) display quite different patterns of induced sister-chromatid exchange (SCE). One, an SV40-transformed Indian muntjac cell (SVM), shows extremely high frequencies of SCE after UV; induced exchanges can be measured after UV doses as low as 0.01 J/m2. This cell also displays exaggerated levels of induced and spontaneous chromosome aberrations. By contrast SCE rates in the Chinese hamster cell mutant, UV-1, are essentially normal. In both SVM and UV-1, however, there is a clear correlation between the cell density and spontaneous frequencies of SCE, a feature which could be related to the observed density-dependent rate of DNA maturation.