Molecular analysis of radiation-induced mutations of the hprt gene in hamster cells

In the late 1970s the authors initiated an extensive study of independent and representative mutants of the hprt gene in V79-4 hamster cells. In summary of biochemical, cytogenetic and reversion analyses the authors inferred that the majority of radiation-induced mutants suffered large genetic changes, while many spontaneous mutants and probably all EMS-induced mutants carried small ('point') mutations of the hprt gene. Molecular analyses of DNA and RNA have now consolidated these findings. Hybridization of DNA from mutant and wild type cells to a hamster hprt DNa probe showed that about 70% of γ-ray or α-particle-induced mutants have extensive gene deletions/rearrangements, and nearly half sustained total loss of hprt gene sequences. In contrast, less than 20% of spontaneous mutants have shown large genetic changes, with about 12% having complete deletion of the hprt gene. Experiments are in progress to define the extent of radiation-induced large deletions and to characterize specific mutants in detail