The announcement in June 2000 that a first draft of the human genome had been completed was rightly recognised as a landmark in scientific endeavour. Predictions were that the sequencing of the genome would allow for the pinpointing of genes responsible for conditions such as Alzheimer’s and heart disease, and lead to finely targeted, even personalised, treatments for a range of disorders. That these ambitions are still some way from being met doesn’t make the discovery any less remarkable. The Human Genome Project (HGP) gave us the capacity to read the basic building blocks of life. Research into the human genome is teaching us that the relationship between our approximately 30,000 genes and who we are is enormously complex, the result not merely of the action of individual genes but also of the ways in which those genes interact with each other and with their environment.