Editing Germline mutation (section)

===Male germline===

In mice and humans the spontaneous [[mutation rate]] in the male germ line is significantly lower than in [[somatic cell]]s.<ref name = Aitken2023>Aitken RJ, Lewis SEM. DNA damage in testicular germ cells and spermatozoa. When and how is it induced? How should we measure it? What does it mean? Andrology. 2023 Jan 5. doi: 10.1111/andr.13375. Epub ahead of print. PMID 36604857</ref>  Furthermore, although the spontaneous mutation rate in the male germ line increases with age, the rate of increase is lower than in somatic tissues.  Within the testicular [[spermatogonium|spermatogonial]] stem cell population the integrity of [[DNA]] appears to be maintained by highly effective [[DNA damage (naturally occurring)|DNA damage]] surveillance and protective [[DNA repair]] processes.<ref name = Aitken2023/>  The progressive increase in the mutation rate with age in the male germ line may be a result of a decline in the accuracy of the repair of DNA damages, or of an increase in [[DNA replication]] errors. Once [[spermatogenesis]] is complete, the differentiated spermatozoa that are formed no longer have the capability for DNA repair, and are thus vulnerable to attack by prevalent oxidative free radicals that cause oxidative DNA damage. Such damaged [[spermatozoon|spermatozoa]] may undergo programmed cell death ([[apoptosis]]).<ref name = Aitken2023/>