SOUTHERN BLOT AND POLYMERASE CHAIN-REACTION EXON ANALYSES OF HPRT(-) MUTATIONS INDUCED BY RADON AND RADON PROGENY

A linear dose response was observed for radon-induced mutations at the CHO-hprt locus with an induction frequency of 1.4 x 10(-4) mutants pe r viable cell per gray. Mutants isolated after two levels of radon exp osure were evaluated using Southern blot techniques and polymerase cha in reaction (PCR) exon amplification. No significant differences in mu tational spectra were detected at these two exposure levels. Of 52 rad on-induced mutations, 48% sustained a gene deletion, 23% underwent a r earrangement of the banding patterns or loss of one or more exons, and 29% showed no change from the parental line. These mutants were compa red with mutants produced after X irradiation (3 Gy) and with spontane ous mutants from untreated cells. The spectra of mutation types in cel ls treated with radon and X rays were not significantly different. In contrast, 31 spontaneous mutations exhibited a low percentage of gene deletion events (16%); most spontaneous mutants showed no change (74%) ; the remaining 10% were classified as alterations. In conclusion, the principal lesion seen at the CHO-hprt locus after radiation exposure is gene deletion, while the predominant class of spontaneous mutations is composed of smaller events not detectable by Southern blot or PCR exon analysis.