In normal basepairing of DNA, the 2’-deoxyguanosine (dG) nucleotide will only pair with 2’-deoxycytidine (dC). Reactive oxygen species produced constantly by radiation, chemical carcinogens and as byproducts of respiration can oxidize the C8 position of dG, forming 8-oxo-2’-deoxyguanosine (OdG). OdG can then form stable base pairs with both dC and 2’-deoxyadenosine (dA). When a dA opposite OdG is replicated, it will be paired to dT rather than dG, causing a dG→dT mutation in the DNA code. These mutations have been linked to diseases such as arthritis, lupus and cancer.