Reactive oxygen species and physical damage cause endogenous damage to DNA. This makes DNA oxidized, have crosslinked bases, physical damage, and can lead to polymerase errors. Endogenous damage is repaired by homologous and non-homologous end joining. In homologous end joining, broken DNA uses the sister chromatid as a template to repair the broken strand. This allows for a complete repair without the loss of genetic material. In nonhomologous end joining, there is no sister chromatid available so the broken ends are cleaned up with an exonuclease and snapped back together with ligase.
Recent comments