In a study of PBMCs from 105 AD patients and 130 controls, the polymorphisms of c.580C>T and c.1196A>G of XRCC1 and c.977C>G of OGG1 are significantly associated with AD risk (Table 2) [216]; both XRCC1 and OGG1 function in BER (Figure 3). Here, XRCC1 is linked to Alzheimer disease.