How do free radicals from carcinogens affect dna in cells?

By definition, free radicals are any molecular specie capable of independent existence that contains an unpaired electron in an atomic orbital.

Explanation: Free radicals are highly reactive species, capable in the nucleus and in the membrane of cells of damaging biologically relevant molecules such as DNA, proteins, carbohydrates, and lipids.

Mutagenesis through oxidative DNA damage is a frequent event in a normal human cell. Oxygen Free Radicals (OFR) plays an important role in the expansion of tumor clones. OFR attack the deoxyribosyl backbone of DNA. Endogenous DNA lesions are genotoxic and induce mutations. This lesions are relatively formed and is mutagenic, therefore, a potential biomaker of carcenogenesis.