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.

8-oxo-2’-deoxyguanosine (OdG), a mutated form of the DNA nucleotide 2’-deoxyguanosine (dG), is formed when dG is oxidized at the C8 position by reactive oxygen species. dG base pairs with 2’-deoxycytosine (dC), promoting correct DNA replication, but OdG can base pair with both dC and 2’-deoxyadenosine (dA). If OdG is paired with dA, the subsequent round of replication results in a point mutation, specifically a dG to dT transversion.