DNA adduct

In molecular genetics, a DNA adduct is a piece of DNA covalently bonded to a (cancer-causing) chemical. This process could be the start of a cancerous cell, or carcinogenesis. DNA adducts in scientific experiments are used as biomarkers of exposure and as such are themselves measured to reflect quantitatively, for comparison, the amount of carcinogen exposure to the subject organism, i.e. rats or other living animals. Under experimental conditions for study, such DNA adducts are induced by known carcinogens, of which commonly used is DMBA (7,12-dimethylbenz(a)anthracene). For example, the term "DMBA-DNA adduct" in a scientific journal refers to a piece of DNA that has DMBA attached to it. The presence of such an adduct indicates prior exposure to a potential carcinogen, but does not by itself indicate the presence of cancer in the subject animal.

Examples
Chemicals which form DNA adducts include: DNA adducts include: By-products include:
 * acetaldehyde, is a significant constituent of tobacco smoke
 * cisplatin binds to DNA and causes crosslinking, leading to death of the cell
 * DMBA (7,12-dimethylbenz(a)anthracene)
 * malondialdehyde, a naturally occurring product of lipid peroxidation
 * etheno-DNA adducts: 1,N(6)-etheno-2'-deoxyadenosine (epsilondA) and 3,N(4)-etheno-2'-deoxycytidine (epsilondC)
 * M1G, a by-product of base excision repair (BER) of a specific type of DNA adduct called M1dG.

DNA Damage
When a chemical bonds to DNA, the DNA becomes damaged, and proper and complete replication cannot occur to make the normal intended cell. This could be the start of a mutation, or mutagenesis, and without proper DNA repair (DNA repair happens naturally under normal circumstances), this can lead to carcinogenesis, the beginnings of cancer.