Cloning
An experimental technique has been developed for cloning certain higher animals. This process involves destroying the nucleus of an egg cell of the species to be cloned. The nucleus is then removed from a body cell of an animal of the same species. This donor nucleus is injected into the egg cell. The egg, with its new nucleus, develops into an animal with the same genetic makeup as the donor. If a number of eggs receive transplants from the same donor, the offspring form a clone. Scientists used this technique to clone such amphibians as frogs and salamanders as early as the 1950's. In 1996, a group led by Scottish scientist Ian Wilmut used the procedure to clone a sheep. They named the clone "Dolly." This event marked the first time a mammal had been cloned in this way.
Excerpt from the "Clone" article, The World Book Encyclopedia © 1999