Recombinant DNA molecules comprising a regulatory element that activates gene expression in response to DNA damage operatively linked to a DNA sequence that encodes a light emitting reporter protein, recombinant vectors containing such DNA molecules and cells containing the DNA molecules or recombinant vectors. A method of detecting for the presence of an agent that causes or potentiates DNA damage is also disclosed which involves subjecting the above-described cells to a putative DNA damaging agent and monitoring the expression of the light emitting reporter protein from the cell.