A CHARACTERISTIC OF MUTANTS INDUCED BY TH E ONCOGENE C-HA-RAS1 AND THE NATURE OF THE MUTAGENIC EFFECT OF THE ONCOGENE

Chinese hamster cell clones of independent origin, which were resistan t to purine base analogs and induced by the activated c-Ha-ras1 oncoge ne, were isolated. It was shown that the isolated clones stably retain ed resistance after cultivation on a medium without an analog, confirm ing mutational nature of the resistance. Most of the clones are able t o grow on the HAT medium, retaining partial activity of the hypoxanthi ne phosphoribosyltransferase enzyme (HPRT); i.e., they are leaky mutan ts. Analysis by blot-hybridization did not reveal the presence of huma n ras-sequences in any of the mutants studied, Evidently, the mutageni c action of the oncogene is not insertional, and resistance is not lin ked to the stably integrated oncogene. The mutagenic effect of c-Ha-ra s1 is likely to be of the ''hit-and-run'' type.