Repair of DNA

Definition

The repair of DNA comprises a group of distinct biochemical pathways by which various types of damage to the DNA, especially damage to the nitrogenous bases A, T, C, and G, is repaired. Such damage can occur spontaneously in living cells as the result of the generation of products of oxidative metabolism that interact with the bases of DNA. Base damage in DNA also transpires as the result of interactions between environmental agents, especially cancer-causing chemicals, with DNA. DNA repair of base damage can be conveniently classified as follows.

Characteristics

Reversal of Base Damage

This mode of DNA repair involves the direct reversal of selected types of base damage. A good example is the restoration of thymine dimers in DNA to their native monomeric state. Thymine dimers (T↔T) are formed by the abnormal chemical joining of adjacent thymine bases (T, T) in DNA and frequently occurs in cells that are exposed to ultraviolet (UV) radiation, such as sunlight. These lesions...