title: Radiation-induced chromosome damage in X-ray-sensitive mutants (xrs) of the Chinese hamster ovary cell line.
abstract: The frequency of both spontaneous and X-ray- (95 rad) induced cytogenetical aberrations has been determined for 2 X-ray-sensitive strains (xrs-6 and xrs-7) of the Chinese hamster ovary cell line, and their wild-type parent (CHO-K1). Increased levels of spontaneous aberrations were not a general feature of the xrs strains, although xrs-7 did show a 2-fold increase in chromatid gaps. Unsynchronied populations of xrs cells, estimated to have been irradiated in late S and G2, showed a 3-5-fold increase in chromatid gaps, breaks and exchanges compared to CHO-K1. The irradiation of synchronised populations of xrs-7 and CHO-K1 in G1 demonstrated a 3-5-fold increase in chromosome breaks, gaps and exchanges in xrs-7. In addition xrs-7 displayed a large increase in chromatid-type aberrations, particularly triradials. These X-ray-sensitive strains have previously been shown to have a defect in double-strand break rejoining (Kemp et al., 1984), and an increased number of double-strand breaks (DBSs) remain in their DNA after irradiation compared to wild-type cells. The increased number of DSBs remaining in these strains 20 min after irradiation, correlates well with the increase in chromosome breaks.
mesh_terms: D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D002842:Chromatids / Q000528:radiation effects; D002869:Chromosome Aberrations; D002875:Chromosomes / Q000528:radiation effects; D006224:Cricetinae; D003412:Cricetulus / Q000235:genetics; D004260:DNA Repair; D005260:Female; D005347:Fibroblasts / Q000528:radiation effects* / Q000648:ultrastructure; D010053:Ovary; D014965:X-Rays