title: The repair of double-strand breaks in the nuclear DNA of Saccharomyces cerevisiae and its genetic control.
abstract: With the use of neutral sucrose sedimentation techniques, the size of unirradiated nuclear DNA and the repair of double-strand breaks induced in it by ionizing radiation have been determined in both wild-type and homozygous rad52 diploids of the yeast Saccharomyces cerevisiae. The number average molecular weight of unirradiated DNA in these experiments is 3.0 X 10(8)+/-0.3 Daltons. Double-strand breaks are induced with a frequency of 0.58 X 10(-10) per Daltonkrad in the range of 25 to 100 krad. Since repair at low doses is observed in wild-type but not homozygous rad52 strains, the corresponding rad52 gene product is concluded to have a role in the repair process. Cycloheximide was also observed to inhibit repair to a limited extent indicating a requirement for protein synthesis. Based on the sensitivity of various mutants and the induction frequency of double-strand breaks, it is concluded that there are 1 to 2 double-strand breaks per lethal event in diploid cells incapable of repairing these breaks.
mesh_terms: D002499:Centrifugation, Density Gradient; D003037:Cobalt Radioisotopes; D004247:DNA / Q000032:analysis*; D004260:DNA Repair; D004171:Diploidy; D005720:Gamma Rays; D006720:Homozygote; D008970:Molecular Weight; D009154:Mutation; D011831:Radiation Genetics; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000528:radiation effects*
chemical_list: D003037:Cobalt Radioisotopes; D004247:DNA