A, B and C. Analysis of sensitivities of single and double mutant strains to increasing concentrations of MMS (A). Approximately 100 cells from mutant and wild type strains were plated on the medium, containing methyl methanesulfonate (MMS) or hydroxyurea (HU) at concentrations given above the columns, or were exposed to UV irradiation at the indicated intensities. The plates were incubated at 33°C until colonies were formed. Strain names are as follows wt (JZ60), swi7-1 (JZ487 or JZ468), rad13 (SV66), mag1 (AM006), rev3 (SV54), rad2 (SV59), swi7rad13 (MK130), swi7mag1 (MK175), swi7-1 rev3 (MK190), swi7-1 rad2 (MK125). B. Survival of wt, swi7-1, rad2 and swi7-1 rad2 strains exposed to MMS. Logarithmically growing cultures were incubated in the presence or absence of 0.03% MMS. Samples were taken at indicated time points, and dilution series of cells for each culture were plated on YEA media and incubated at 33°C until colonies formed. The survival is shown as the relative percentage compared to the values obtained using the untreated starting cultures.