Describe the process and the role of DNA repair

Proof reading - polymerase detects and correct it 99% of the times Nucleotide mismatch repair - reduces error rate after DNA replication ' - mismatched bases are detected by an enzyme and is is replaced Base excision repair and Nucleotide excision repair - repair single stranded DNA damage caused by external agents e.g.) UV or endogenous factors such as reactive oxygen species - two repair mechanisms are distinct Double strand break repair - Happens when both DNA strands are broken which may result in chromosomal rearrangement