Base Excision Repair (BER)

The steps and some key players:

1. Removal of the damaged base (estimated to occur some 20,000 times a day in each cell in our body!) by a DNA glycosylas
2. We have at least 8 genes encoding different DNA glycosylases each enzyme responsible for identifying and removing a specific kind of base damage
3. Removal of its deoxyribose phosphate in the backbone, producing a gap. We have two genes encoding enzymes with this function
4. Replacement with the correct nucleotide. This relies on DNA polymerase beta, one of at least 11 DNA polymerases encoded by our genes
5. Ligation of the break in the strand. Two enzymes are known that can do this; both require ATP to provide the needed energy.