There are four major ways to repair the damaged DNA;
- Base Excision Repair(BER)
- Nucleotide Excision Repair(NER)
- Mismatch Repair(MMR)
- SOS Repair
Base Excision Repair(BER)
This type of repair is used to fix small sized damages that do not distort the helical structure of the DNA molecule.
- It is done by enzymes known as glycosylases that recognize the damaged base and remove it.
- After this, AP endonucleases are recruited to cleave AP sites.
- DNA polymerase adds the missing bases and they are joined together by ligase.
Examples of such damages are deamination, oxidization or alkylation of a base.