In this study, to explore the role of p53 in radiation carcinogenesis in a model system with intact p53, we use transgenic mice that harbour an inducible in vivo shRNA against p53 (ref. 17) to ask a reciprocal question: what happens to tumour development when p53 is temporarily turned off during irradiation in p53 WT mice? The gene discussed is TP53; the disease is neoplasm.