DNA strand breaks, repair, and survival in x-irradiated mammalian cells.
The yields of unrepairable single-and double-strand breaks in the DNA of x-irradiated Chinese hamster cells were measured by low-speed neutral and alkaline sucrose density gradient sedimentation in order to investigate the relation between these lesions and reproductive death. After maximal single-strand remoining, at all doses, the number of residual single-strand breaks was twice the number of residual double-strand breaks. Both double-strand and unrepairable single-strand breaks were proportional to the square of absorbed dose, in the range 10-50 krad. No rejoining of double-strand breaks was observed. These observations suggest that, in mammalian cells, most double-strand breaks are not repairable, while all single-strand breaks are repaired except those that are sufficiently close on complementary strands to constitute double-strand breaks. Comparison with cell survival measurements at much lower doses suggests that loss of reproductive capacity corresponds to induction of approximately one double-strand break.
D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects*; D004247:DNA / Q000032:analysis / Q000528:radiation effects*; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D008970:Molecular Weight; D011830:Radiation Effects; D014965:X-Rays
D004247:DNA