UV Intensity and Duration of Exposure Affects the Reversion Frequency of hisG46 in Salmonella typhimirium TA100

Ultraviolet (UV) radiation has been shown to be a potent mutagen of DNA. Photocarcinogenesis is caused largely by mutations at sites of incorrectly repaired DNA photoproducts, of which the most common is the thymine dimer. Whether the total dose is the critical causative agent or if the conditions of exposure play a role in the mutagenesis has not been established. Total dose is dependent on the total time of exposure and the distance from the source of radiation. The purpose of this experiment was to determine whether UV radiation delivered with high intensity for a short duration is more mutagenic than that delivered with a low intensity for a long duration if both conditions result in the same total dose. The reversion frequency of hisG46 in Salmonella typhimurium TA100 was used as a model to determine the mutagenic effects of different UV conditions. A range of total doses -2 -2 from 36 Jm to 158 Jm of UVC (254 nm) were compared by varying conditions of intensity and duration. The results of these comparisons show that UV doses of high intensity, short durations are more mutagenic than those of low intensity, long duration doses.