Nucleic acids (DNA and RNA) carry the genetic information of living organisms in the form of units called genes. Each gene consists of a specific sequence of buildings units called nucleotides that code for making proteins that are essential for our general growth, development and reproduction. Therefore, any disruption in genetic materials will lead to serious complications and diseases that may lead to the death of the organism. Disruption in the genetic material of most living organisms (DNA) can occur by two main types of factors: exogenous factors such as environmental agents (chemicals, radiation and pollutants) and endogenous factors such as highly reactive molecules that are produced within body during metabolic processes. Either exogenous or endogenous factors can damage DNA but the endogenous factor is the most dangerous factors. Fortunately, various induced DNA can be distinguished and repaired by different repair mechanisms that try to fix induced exogenous or endogenous DNA damage. Consequently, the different types of induced DNA damage and various mechanisms of DNA repair will be discussed in the manuscript.