cdA was also present in the brains of the XP group A gene-knockout (Xpa−/−) and significant accretion were detected in mice at 6, 24, and 29 months of age, compared to wild-type animals, through an improved enzyme-linked immunosorbent assay (ELISA) [15] using a novel monoclonal antibody (cdA-1) specific for cdA in single-stranded DNA [58]. The gene discussed is CDA; the disease is xeroderma pigmentosum.