DNA metabolism (causes DNA damage)

Missing base

due to removal of pruines by acid or heat or removal of alteed bases by DNA glycosylases

Altered base

due to ionizing radiation

incorrect base

due to mutations affecting 3’ → 5’ exonuclease proofreading or incorrectly incorporated bases

bulges due to deletion or insrtion of nt

due to intercalating agenst that cause addition or loss of nt during recombination/replication

linked pyrimidines

due to dimers resulting from UV radiation

ss/ds breaks

due to breakage of phosphodiester bonds by ionizing agents or chemical agents

cross-linked strands

due to covalent linkage of two strands by bifunctional alkylating agents

3’ deoxyribose fragments

due to disruption of deoxyribose ring structure by free radicals