Dna Damage and Repair
The long, thin DNA molecules contain three components: nitrogen-rich bases, sugar groups, and phosphate groups. The composition of the four types of bases—adenine, guanine, cytosine, and thymidine—makes up the genetic code. Damage to DNA can occur to any of its three components. The bases are the most reactive, and there is far more knowledge about changes to them than to the sugar or phosphate components of DNA. Also, many chemicals or carcinogens form adducts (lesions) with new chemical groups being attached to existing DNA bases.