The human genome consists of about 3 billion genetic building blocks, and researchers around the world are working on its decoding. This book provides understandable and up-to-date information about the most important research projects and their results. It shows which hopes for the medical application of genetic research have been fulfilled so far, where genetic tests and gene therapies are currently possible, and where they may be developed in the near future. A critical discussion addresses the issue of gene patenting and the potential discrimination of individuals and ethnic groups through genetic testing. Selected examples illustrate how genes can provide insights into evolution. The book concludes with a comprehensive glossary explaining important technical terms.