Abstract

On Sunday morning, 23 February 1997, the world awoke to a technological advance that shook the foundations of biology and philosophy. On that day, we were introduced to Dolly, a 6-month-old lamb that had been cloned directly from a single cell taken from the breast tissue of an adult donor. Perhaps more astonished by this accomplishment than any of their neighbors were the scientists who actually worked in the field of mammalian genetics and embryology. Outside the lab where the cloning had actually taken place, most of us thought it could never happen. Oh, we would say that perhaps at some point in the distant future, cloning might become feasible through the use of sophisticated biotechnologies far beyond those available to us now. But what many of us really believed, deep in our hearts, was that this was one biological feat we could never master. New lifemust have its origins in an embryo formed through the merger of gametes from a mother and father. It was impossible, we thought, for a cell from an adult mammal to become reprogrammed, to start all over again, to generate another entire animal or person in the image of the one born earlier