title: Lethal sectoring is not the basis for EMS-induced pure mutant clones in Chinese hamster cells.
abstract: Treatment of G1-synchronized mammalian cells with mutagenic agents which act on one strand of the DNA at a given site would be expected to produce colonies containing both mutant and wild-type cells (mosaic). We have observed that in addition to mosaic colonies, G1-synchronized Chinese hamster ovary cells which had been treated with the single-strand mutagen ethyl methanesulfonate (EMS), produced colonies in which all the cells lacked glucose-6-phosphate dehydrogenase activity. These completely mutant (pure) colonies could be derived from a potentially mosaic colony by the "death" of the wild-type cell after the first cell division, leaving only the glucose-6-phosphate dehydrogenase (G6PD)-deficient cell to grow into a colony (lethal sectoring). Using time-lapse photography to analyze cell lineages after EMS treatment, we find that cell lysis, cell release, cell migration, or proliferative failure of one lineage at the 2-cell stage accounts for only 20-25% of the pure mutant colonies observed. This result suggests that in the Chinese hamster cell there exists a mutational mechanism which fixes the mutation in both strands of the DNA before the next replication cycle following EMS treatment.
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002999:Clone Cells; D006224:Cricetinae; D003412:Cricetulus; D005020:Ethyl Methanesulfonate / Q000633:toxicity*; D005260:Female; D009154:Mutation; D010053:Ovary
chemical_list: D005020:Ethyl Methanesulfonate