The effect of caffeine on survival of UV-irradiated diploid yeast strains of different sensitivities.

The action of caffeine post-treatment after UV exposure in three strains of diploid yeast has been studied. The addition of the drug to the plating medium reduced survival in all cases. Higher colony-forming abilities were found in all strains when the UV dose had been split into two fractions with an interval of about 6 h. Caffeine added to the incubation medium between dose fractions did not interfere with this process in the wild type but suppressed split-dose sparing completely in two sensitive strains.