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. 2021 Apr 6;80(3):1119–1128. doi: 10.3233/JAD-200620

Fig. 1.

Fig. 1

Natural defenses act against endogenous DNA damage. A 100 kg person contains about 1014 cells (avg. cell wt.∼10-9 g). Free radical production would cause∼109 DNA alterations per cell per day; however, antioxidant production lowers the actual rate to∼106 DNA alterations per cell per day. The damage-repair defense lowers the incidence of persistent DNA alterations to∼102 per cell per day, and the damaged-cell removal defence results in the natural occurrence of one mutation per cell per day. (The ratio of metabolic DNA damage to radiation-induced DNA damage by 0.1 cGy/year natural background radiation is about 10 million.) Reprinted with permission from Pollycove M, Feinendegen LE [13], © 2003 SAGE Publications and adapted for this publication.