Base Excision Repair(BER):
1. DNA glycosylases cleave the N-glycosidic bond and generate AP sites (Abasic sites). Different DNA glycosylases are used to remove different damaged bases.
2. AP endonucleases cleave the DNA at the site of damage.
3. dRpase (Deoxyribophosphodiesterase) removes several sugar-phosphate residue.
4. DNA polymerase inserts new stretch of DNA and the gap is sealed by DNA ligase.