SOUTHERN ANALYSIS OF GENOMIC ALTERATIONS IN GAMMA-RAY-INDUCED APRT^- HAMSTER CELL MUTANTS

Andrew J. Grosovsky ¹, Elliot A. Drobetsky ¹, Pieter J. deJong ², and Barry W. Glickman ¹

¹ York University, Department of Biology, Toronto, Ontario M3J 1P3, Canada
² Laboratory of Genetics, National Institute of Enviromental Health Sciences, Research Triangle Park, North Carolina 27709

The role of genomic alterations in mutagenesis induced by ionizing radiation has been the subject of considerable speculation. By Southern blotting analysis we show here that 9 of 55 (approximately 1/6) gamma-ray-induced mutants at the adenine phosphoribosyl transferase (aprt) locus of Chinese hamster ovary (CHO) cells have a detectable genomic rearrangement. These fall into two classes: intragenic deletions and chromosomal rearrangements. In contrast, no major genomic alterations were detected among 67 spontaneous mutants, although two restriction site loss events were observed. Three gamma-ray-induced mutants were found to be intragenic deletions; all may have identical break-points. The remaining six gamma-ray-induced mutants demonstrating a genomic alteration appear to be the result of chromosomal rearrangements, possibly translocation or inversion events. None of the remaining gamma-ray-induced mutants showed any observable alteration in blotting pattern indicating a substantial role for point mutation in gamma-ray-induced mutagenesis at the aprt locus.

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