More than 9 out of 10 Alzheimer's cases could be driven by specific variations in a single gene and the protein it produces, a new study reveals, suggesting that treatments targeting this well-known gene could prevent the disease from developing in the majority of instances. The gene in question, APOE , has long been associated with Alzheimer's risk. What's new here is the way the different variations of the gene have been analysed and mapped against the chances of developing Alzheimer's. It