Genotoxic impurities of pharmaceutical products or genotoxic chemicals exert their adverse effects through interaction with genomic DNA of cells. Genetic toxicology tests are designed to detect drugs which can induce genetic damage directly or indirectly by various mechanisms. Compounds that are identified as genotoxic in these tests have the potential to be human carcinogens and/or mutagens, and ultimately may induce cancer and/or heritable defects.