For example, ROS generated by ionizing radiation can inactivate essential DNA repair proteins, including the MRN complex, DNA-PK, and DNA repair helicase such as xeroderma pigmentosum group D(XPD) and fanconi anemia complementation group J (FANCJ) [85,88,89]. The gene discussed is PRKDC; the disease is xeroderma pigmentosum group D.