DNA damage can be subdivided into two types: (1) endogenous damage caused by reactive oxygen species (ROS) that are derived from metabolic byproducts and (2) exogenous damage caused by radiation (UV, X-ray, gamma), hydrolysis, plant toxins, and viruses.

Un-repaired DNA damage accumulates in non-replicating cells, such as neurons or myocytes of adult mammals, and can cause aging. While most DNA damage can be repaired, such repair systems are not 100% efficient. While DNA damage is distinguished from mutation, mutation can result from unrepaired DNA. Moshe Arditi, in Biological DNA Sensor, 2014ĭNA damage exists in all cellular organisms.