Credit: P. JOYCE

Passengers travelling from London to Cambridge by train may glimpse this striped cycle path cutting through the flat countryside as they near their destination. Over a mile of its length, different coloured bands spell out the base-pair sequence of the BRCA2 gene — mutations in which are associated with increased risk of breast cancer.

The path includes the UK cycle network's ten thousandth mile. John Sulston, director of the Cambridge Sanger Centre during its work on the Human Genome Project, and a keen cyclist, helped develop the idea of decorating it with a gene.

BRCA2 was picked because the gene contains about 10,000 base pairs, echoing the cycle network's celebratory theme. But there were other reasons, too. As a predictor of disease and the subject of a patent dispute, BRCA2 highlights some of the social issues that surround gene sequencing.

“I expect this will be one of only a few human genes to be represented as a cycle path,” says Michael Stratton, who identified and mapped BRCA2 twelve years ago and acted as a scientific advisor to this project. It's a safe bet — were the entire human genome laid down at the same scale, the path would circle Earth about ten times.

J.H.