This book is about mobile genes-the transfer of DNA between unrelated cells. It discusses the machinery of gene transfer and its wide-ranging biological and health consequences. Mobile DNA makes possible the development of antibiotic resistance in microbes, the conversion of harmless to pathogenic bacteria, and the triggering of cancerous growth in cells. It also contributes to human evolution. This well-illustrated volume contains an up-to-date account of a topic now seen as increasingly important, and will be invaluable for both working scientists and as a textbook for advanced courses.