50,000 - 200,000 lesions
||Gangloff S, Arcangioli B. DNA repair and mutations during quiescence in yeast. FEMS Yeast Res. 2017 Jan 1 17(1). doi: 10.1093/femsyr/fox002. p.4 left column 3rd paragraphPubMed ID28087675
||Nakamura J, Swenberg JA. Endogenous apurinic/apyrimidinic sites in genomic DNA of mammalian tissues. Cancer Res. 1999 Jun 1 59(11):2522-6.PubMed ID10363965
||Primary source abstract: "Apurinic/apyrimidinic (AP) sites are one of the most frequent lesions in DNA. Using a highly sensitive slot blot assay, [investigators] determined the number and condition of endogenous AP sites in normal tissues of rats and human liver. The number of AP sites (50,000-200,000 per mammalian cell) was greatest in brain, followed by colon and heart, and then liver, lung, and kidney. The majority of endogenous AP sites were cleaved 5' to the AP site. These data suggest that removal of the deoxyribosyl phosphate moiety is the rate-limiting step in base excision and AP site repair in vivo."
||P.4 left column 3rd paragraph: "An abasic site (AP) site is formed when a base is lost from the DNA by cleavage of an N-glycosyl bond, leaving the sugar-phosphate chain intact (Friedberg et al.2005). At normal physiological conditions, it has been estimated that 50,000–200,000 AP site lesions persist at a steady-state level in mammalian cells (primary source). Abasic sites are potentially mutagenic and can be produced by a spontaneous loss of bases from DNA. Abasic sites can also be produced by ROS [Reactive oxygen species](Nakamura and Swenberg 1999), as well as being produced in intermediate steps of the base excision repair (BER) pathway. Inefficient or incomplete BER might leave abasic sites in DNA."