When it comes to understanding a disease as complex as Alzheimer's, the more the better - genes, that is. In September, 15 years since the last discovery of its kind, scientists finally identified a new set of genes that may contribute to the memory-robbing disorder. Two groups of researchers, working separately, homed in on three genes linked to the late-onset form of the disease, the type that hits people in their 60s or later and accounts for 90% of Alzheimer's cases in the US. Two of the genes are known to interact with the amyloid-protein plaques that build up in the brain of Alzheimer's patients and eventually cause nerve-cell death and cognitive problems. The third affects the junction of nerve cells, where various neurochemicals work to relay signals from one nerve cell to another.