In an elegant study on volunteers over time, the authors sought for associations between p53 activity and measured UV-induced DNA damage via cyclobutane pyrimidine dimers (CPDs), since p53-mediated excision repair of UV-induced DNA damage is a critical effector in xeroderma pigmentosum (XP) and in photoproduct-related skin cancer. The gene discussed is TP53; the disease is xeroderma pigmentosum.