## DNA damage - a potential source of mutations

The discovery of the structure of DNA and the subsequent detailed knowledge of this molecule have revealed an indisputable fact: DNA is a very dynamic molecule that is constantly undergoing changes. These changes result from its chemical nature but are also caused by the environment in which DNA resides within the cell. In addition, changes to DNA can also be caused by external factors (Figure 5.2), which include ionizing radiation as used by Muller in his experiments with flies. These changes are collectively called DNA damage and are a potential source of mutations. The process by which DNA damage becomes a mutation is usually a multistep process, and cells have many ways to reverse it and maintain the integrity of the DNA molecule.