DNA damage

Our genetic material is under constant attack from radiation and chemicals. Damage accumulates and causes cells to malfunction. This can be corrected in several ways. First, cells other than neurons that are malfunctioning can usually be killed; the body will replace them with no ill effects. In fact, cells contain several mechanisms for killing themselves if they detect that they are not working right. (Stem cells and other techniques can help if the body is slow to replace the missing cells.) Second, it should be possible to minimize damage by vacuuming up the chemicals that cause mutation, and by manipulating the cell's state to increase the amount of energy it spends on self-repair. Third, a nanomachine may scan each cell's DNA to search for and repair damage, or perhaps simply replace chromosomes periodically with new error-free copies.