Mutagens are chemicals or physical factors (such as radiation) that increase the rate of mutation in the cells of bacteria, plants, and animals (including humans). In the living cell, DNA undergoes frequent chemical change, especially during replication. Most of these changes are quickly repaired. Those that are not, result in a mutation. Accordingly, one form of mutation results from a failure of DNA repair. Most mutagens are of natural origin. Mutagenesis is a DNA replication failure that results in a mutation. Mutagenesis may occur as a result of a mutatgen, or occur spontaneously.

Mutagens can be found throughout nature. Very small doses of a mutagen usually have little effect while large doses of a mutagen could be lethal. DNA in the nuclei of all cells encodes proteins, which play important structural and functional (metabolic) roles in the cell. Mutagens typically disrupt the DNA of cells, causing changes in...