DNA technology is on the verge of a revolution. At the moment, it is both time-consuming and expensive to study different versions of genes. But soon, scientists will be able to look at different alleles of many genes at once, using new technologies such as DNA chips. In the future, doctors may offer DNA chip 'gene screens' to people at risk of certain illnesses, such as heart disease or cancer. This will help identify anyone who may benefit from drug treatment or a change of lifestyle.