Identifying genes that increase the risk of bowel or other cancers allows us to offer preventative measures, such as removing tumours at an early stage. A better understanding of how and why cancers grow also helps develop improved treatments. Ian Tomlinson, Professor of Molecular and Population Genetics at the Wellcome Trust for Human Genetics, works on the identification of genes that predispose to colorectal and other cancers. His research focuses on the relative importance of selection and genomic instability.