Prof Arnold Levine speaks about his work investigating the p53 gene and p53 protein. Cancer is often caused by mutation of a number of genes. Prof Levine explains how inactivation of these mutated genes can stop the cancer and describes how the p53 gene contributes to cancer prevention by maintaining the fidelity of information transfer in somatic cells. The related p63 and p73 genes play a similar role in germline cells; Prof Levine explains how this function can be used to discover additional tumour suppressor genes and to identify patients who have a high probability of developing cancer.