5 DNA damage
The integrity of DNA as a genetic material is of paramount importance to an organism, and a multitude of proteins exist that serve to prevent or reverse damage to the DNA. However, like all biological macromolecules, DNA decomposes spontaneously. The reasons for the ease of decomposition of DNA are intimately linked to the chemical structures of the constituent bases and phosphodiester-linked sugars. The limited stability of DNA may be integral to the molecular basis of evolution. If DNA were extremely stable and its replication perfect, the sequence of bases within a gene would be passed on to each succeeding generation with no alterations. But small chemical changes to DNA that result in alterations to genes do occur, resulting in the variations in protein structure and function that underlie evolution. In this section, we will briefly examine the features of DNA that make it susceptible to damaging agents from both cellular activities and the environment.