This is the first in a four-part series of lectures celebrating the 50th anniversary of Watson and Crick's discovery of DNA in 1953. These lectures explore the impact this breakthrough is having on scientific discovery today. Part I: The human genome project has provided researchers with a growing list of genes; but the key to understanding life, both in health and sickness, is the script that outlines how these cellular players interact with each other. Young discusses how researchers are using new approaches to biology to map out cell circuitry and illuminate the cause of disease.