XRCC4 and hereditary disease: This study, however, did not show significant association for SNPs in CDKN1A, TP53, LIG IV, PRKDC, XRCC3 and XRCC4. These negative results, however, do not negate the importance of these genes to radiosensitivity as mutations in TP53 and LIG IV are well-known example of genetic disorder with potential impact on radiosensitivity.