We look further for biological functions, XPD was found to possess DNA repair capacity (DRC) and studies have found two XPD polymorphisms, XPD Asp312Asn and Lys751Gln, had a modulating effect on DRC and there existed possible association between XPD Asp312Asn and Lys751Gln polymorphisms in lung cancer 37,38]. The gene discussed is ERCC2; the disease is lung carcinoma.