A genetic model for colorectal cancer highlighted key genes, including the tumour suppressor genes adenomatous polyposis coli (APC) and p53 and the oncogene Kirsten-Ras (K-Ras), the progressive acquisition of mutations in which was proposed to regulate the adenoma-carcinoma transition (Vogelstein et al, 1988). The gene discussed is KRAS; the disease is colorectal cancer.