8-Oxo-2'-deoxyguanosine is an oxidized derivative of 2'-deoxyguanosine. It is one of the major products of oxidative DNA damage and is used in mechanistic studies of DNA damage and associated repair. 8-Oxo-dG can be quantified in biological systems as a measure of oxidative stress. 8-Oxo-dG DNA lesions are formed in the cell by reactive oxygen species. These can be present due to normal oxidative metabolic processes, UV ionizing radiation or 2-nitropropane, an industrial solvent and component of tobacco smoke. 8-Oxo-2'-deoxyguanosine-5'-Triphosphate (8-Oxo-dGTP), as well as dPTP, are considered mutagenic dNTPs which can be incorporated into DNA by PCR using standard Taq polymerase. Random mutagenesis is induced by amplification of the target in the presence of the four natural dNTPs plus the mutagenic analogs, 8-Oxo-dGTP and/or dPTP. When both mutagenic analogs are used, the rate of mutagenesis is controlled by the number of PCR cycles, where 6%, 11% and 19% mutagenesis rates are obtained after 10, 20 and 30 cycles, respectively. 8-Oxo-dGTP can mispair with A, leading to A-to-C and G-to-T transversion mutations, which occur in a 1 : 1.5 ratio in PCR. When dPTP is used in combination with 8-Oxo-dGTP in PCR, both transition mutations (A-to-G and G-to-A) and transversion mutations (A-to-C and G-to-T) can be produced.