The authors have developed a text that reflects the directions genetics is taking as it heads into the 21st century. This perspective embraces five major themes: the central importance of the genome, as opposed to the action of individual genes; the application of genetics to the improvement of human health; the growing appreciation for the relationships among organisms arising from genetic research; the impact of biotechnology on the accelerating growth of genetic knowledge; and the importance of emerging social and ethical issues related to our use of biotechnology.