Health 10 December 2012 By Andy Coghlan Nobody’s perfect. Even healthy people have at least 400 faulty genes, including a few that could lead to life-threatening diseases. Chris Tyler-Smith of the Wellcome Trust Sanger Institute in Cambridge, UK, and his colleagues scanned the genomes of 179 healthy men and women from the US, China, Japan and Nigeria. They compared them with a library of 50,000 mutations known to cause disease.