Can you repair DNA damage, or can you only prevent it?

Your body actively repairs DNA damage every single day. Cells are constantly bombarded by harmful influences: from within, by by-products of metabolism, and from outside, by radiation and chemicals. This causes three types of damage: a break in one strand of the DNA, a break in both strands simultaneously, or damage to a single building block. The body has robust repair mechanisms that tackle this damage rather than merely preventing it.

The more severe the damage, the longer the repair takes. Breaks in both strands at once demand far more time from the cell than simpler forms of damage. Moreover, that repair is not always error-free: occasionally a small piece of DNA is permanently lost. Over time, such small losses can contribute to changes in the genetic material. When the repair mechanisms become structurally disrupted, damage accumulates. This is a well-known driver of cancer development.

There is also a flip side. Cancer cells with an especially strong repair capacity fix the DNA damage inflicted by chemotherapy more quickly than normal cells do. That makes the treatment less effective. Researchers are looking for ways to selectively inhibit this repair process in cancer cells.

The genetic material in your cells' energy factories, the mitochondria, is more vulnerable than the DNA in the nucleus. There are indications that this DNA can also be repaired, but exactly how that works is still far less well understood. Ideas about transferring healthy mitochondria as a therapy remain entirely hypothetical. Finally, DNA repair is not an isolated process: the cell's energy balance partly determines how well repair functions. Cellular fatigue, caused for example by ageing or disease, can therefore indirectly weaken the repair capacity.