Because p53 cancer mutations are localised to one region of hotspots (Fig. 1A), repair plasmids covering the majority of hotspots could be synthesised, containing either 1.35 kb or 1.78 kb DNA, homologous to the genomic p53 locus between exons 5–8 or 6–8 (Sequences given in Methods S1). This evidence concerns the gene TP53 and cancer.