Apurinic/apyrimidinic (AP) sites (pre-mutagenic lesions that can prevent normal DNA replication) occur frequently in DNA molecules by spontaneous hydrolysis, by DNA damaging agents or by DNA glycosylases that remove specific abnormal bases.
Apurinic/apyrimidinic (AP) sites (also called "abasic sites") occur frequently in DNA molecules by spontaneous hydrolysis, by DNA damaging agents or by DNA glycosylases that remove specific abnormal bases. AP sites are pre-mutagenic lesions that can prevent normal DNA replication. 
