[Multiple mutants of Saccharomyces cerevisiae. III. The identification of the mutational changes that occur].

Localization and molecular nature of mutations in multiple mutants of yeast Sacchromyces cerevisiae were studied. It was found that simultaneous changes in several genes located in more than five linkage groups took place during the arise of multiple mutants after a single UV-irradiation (at a dose of 300 erg/nm2). It was shown that reversions of original nonsense-mutations were due to mutational changes in the same genes and the arise of the forward nonsense-mutations in the other genes took place as a result of base changes in DNA.