Figure 5.

Effect of Mn²⁺ and Mg²⁺ on the mutation rate of the reversion of the lys2-10A allele. (a) Mutation rates determination by the yeast mutator assay using a strain carrying the lys2-10A allele was performed in the presence of increasing concentrations of Mn²⁺. The appearance of Lys⁺ revertant colonies indicates a mutator phenotype. Rates are calculated as described in Section 2 and standard deviation is included at the top of each bar. (b) Cotreatment with 10 mM Mg²⁺ protects cells from the toxicity of Mn²⁺. Survival was determined as described in Section 2. (c) Cotreatment with 10 mM Mg²⁺ reduces the accumulation of mutations on the lys2-10A allele induced by 1.5 mM Mn²⁺. Each bar corresponds to the average of three sets of experiments using five independent colonies per set.