Cloning is the creation of an individual that is a genetic replica of another individual. The process transfers a nucleus from a somatic nonreproductive cell into an "enucleated" fertilized egg, one that has had its own nucleus destroyed or removed. The genes in the transferred nucleus then direct the development of a complete organism from the altered fertilized egg. Two individuals who are clones have identical genes in their cell nuclei, but differ in characteristics that are acquired in other ways.

Cloning in Context

Cloning is a natural phenomenon in species as diverse as armadillos, poplar trees, aphids, and bacteria. Identical twins are clones. Biologists have been cloning some organisms, such as carrots, for decades. Attempts to clone animals have been far less successful. They began long before the February 1997 announcement of the birth of Dolly, a sheep cloned from a mammary gland cell...