DNA damage is a change in the chemical structure of DNA. It can be a break in a strand of DNA, a chemically changed base like 8-OHdG, or a base missing from the DNA backbone. Natural damage to DNA can result from hydrolytic or metabolic processes. During metabolism, compounds that damage DNA such as reactive oxygen species, reactive carbonyl species, reactive nitrogen species and lipid peroxidation products are released. On the other hand, hydrolysis process weakens chemical bonds in DNA.
Although both DNA damage and mutations are types of error in DNA, they are distinctly different. When a DNA is damaged, its chemical structure is altered. In mutation, alteration occurs in the DNA sequence.
Mutation and DNA damage have different biological consequences. Although many DNA damages are repairable, such repairs are not 100 percent effective. Un-repaired DNA damages mostly accumulate in non-replicating cells (cells in the muscles or brains of adult mammals) and can result in aging. In replicating cells, errors occur during replication. These errors can cause epigenetic alterations or mutations. Both of these alterations can be replicated and eventually passed on to subsequent generations of cells. These alterations can change regulation of gene expression, change gene function and possibly contribute to the development of cancer.