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^[1] 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.^{[citation needed]} 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^[2] .^{[citation needed]}

Examples

Chemicals which form DNA adducts 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^[3]

DNA adducts include:

• etheno-DNA adducts: 1,N(6)-etheno-2'-deoxyadenosine (epsilondA) and 3,N(4)-etheno-2'-deoxycytidine (epsilondC)

By-products include:

• M₁G, a by-product of base excision repair (BER) of a specific type of DNA adduct called M1dG.

DNA Damage

When a chemical binds 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.

See also

• Adduct
• Intercalation (chemistry)

References

1. ^ La, DK; Swenberg, JA (1996). "DNA adducts: biological markers of exposure and potential applications to risk assessment.". Mutation Research/Reviews in Genetic Toxicology 365 (1-3): 129–146. 
2. ^ Farmer, P. "Biomarkers of exposure and effect for environmental carcinogens, and their applicability to human molecular epidemiological studies". Public Health Applications of Human Biomonitoring. U.S. EPA. http://www.epa.gov/ncer/publications/workshop/09_25_07/. Retrieved 22 June 2011. 
3. ^ Lipid peroxidation-DNA damage by malondialdehyde. Marnett LJ.