Respiratory repression and the stability of the mitochondrial genome

The variation in sensitivity of the mitochondrial genome of Saccharomyces cerevisiae to ethidium bromide-induced petite mutation in response to changes in glucose concentration has been studied. Growth in high glucose considerably depressed the mutation rate, whilst small variations are observed in response to step-up or step-down in glucose concentration. Variations in mitochondrial DNA and respiratory activity during the mutagenic process are described. Effects of non-metabolizable sugars which repress mitochondrial biogenesis and a number of antimitochondrial drugs have been investigated. The results are discussed in terms of possible mechanisms of modulation of the mutation rates.