The relationship between DNA damage and repair and the occurrence and development of disease

DNA damage can lead to the development of diseases such as tumors. To counteract this, organisms have evolved various repair mechanisms targeting different types of damage. In eukaryotes, there are four main types of DNA repair: nucleotide excision repair (NER), base excision repair (BER), mismatch repair (MMR), and double-strand break repair (DSB repair). NER can remove large fragments of DNA damage, BER can repair damage to individual bases, MMR is used to repair base mismatch, while DSB repair includes two mechanisms: non-homologous end joining (NHEJ) and homologous recombination (HR). NHEJ directly connects the broken ends without a template, while HR uses intact sister chromatids as repair templates. Studying DNA damage and repair mechanisms can pave the way for developing new clinical drugs.