INCANDESCENT LAMPS CAN PRODUCE PYRIMIDINE DIMERS IN DNA

DNA molecules that have been exposed to light from a 150 W incandescent spot lamp are nicked by the Micrococcus luteus endonuclease specific for cyclobutyl‐type pyrimidine dimers. The production of these enzyme‐sensitive sites increases with increasing spot lamp exposure. These sites have been confirmed to be pyrimidine dimers by their property of being photoreversed by an E. coli photoreactivating enzyme. The emission spectrum of the lamp shows detectable output at wavelengths less than 320 nm. These results indicate that the sensitivity of the techniques utilized in this work can be used to detect low levels of contaminating UV radiation.