clone, group of organisms, all of which are descended from a single individual through asexual reproduction, as in a pure cell culture of bacteria. Except for changes in the hereditary material that come about by mutation, all members of a clone are genetically identical. In 1962 John Gurdon was the first to clone an animal when he transferred cell nuclei from adult frog intestinal cells and injected them into egg cells from which the nucleus had been removed; the eggs then developed into tadpoles. Laboratory experiments in in vitro fertilization of human eggs led in 1993 to the "cloning" of human embryos by dividing such fertilized eggs at a very early stage of development, but this technique actually produces a twin rather than a clone. In a true mammalian clone (as in Gurdon's frog clone) the nucleus from a body cell of an animal is inserted into an egg, which then develops into an individual that is genetically identical to the original animal.

Later experiments in cloning resulted in the development of a sheep from a cell of an adult ewe (in Scotland, in 1996), and since then rodents, cattle, swine, and other animals have also been cloned from adult animals. Despite these trumpeted successes, producing cloned mammals is enormously difficult, with most attempts ending in failure; cloning succeeds 4% or less of the time in the species that have been successfully cloned. In addition, some studies have indicated that cloned animals are less healthy than normally reproduced animals.

In 2001 researchers in Massachusetts announced that they were trying to clone humans in an attempt to extract stem cells. The National Academy of Sciences, while supporting (2001) such so-called therapeutic or research cloning, has opposed (2002) the cloning of humans for reproductive purposes, deeming it unsafe, but many ethicists, religious and political leaders, and others have called for banning human cloning for any purpose. South Korean scientists announced in 2004 that they had cloned 30 human embryos, but an investigation in 2005 determined that the data had been fabricated. In 2013 scientists at Oregon Health and Science Univ. reported that they had created embryonic stem cells using genetic material from human skin cells and donated eggs; the technique used to create the embryo, however, would not result in a viable human clone.

See G. Kolata, Clone (1997).

The Columbia Encyclopedia, 6th ed. Copyright© 2015, The Columbia University Press.

Cloning: Selected full-text books and articles

On Cloning By John Harris Routledge, 2004
The Cloning Sourcebook By Arlene Judith Klotzko Oxford University Press, 2001
The Ethics of Human Cloning By Leon R. Kass; James Q. Wilson AEI Press, 1998
Crafting a Cloning Policy: From Dolly to Stem Cells By Andrea L. Bonnicksen Georgetown University Press, 2002
Human Cloning and the Myth of Disenchantment By Staicu, Laurentiu Journal for the Study of Religions and Ideologies, Vol. 11, No. 31, Spring 2012
Peer-reviewed publications on Questia are publications containing articles which were subject to evaluation for accuracy and substance by professional peers of the article's author(s).
Biotechnology and Communication: The Meta-Technologies of Information By Sandra Braman Lawrence Erlbaum Associates, 2004
Librarian’s tip: Chap. 8 "Biotechnology, Democracy, and the Politics of Cloning"
Things That Count: Essays Moral and Theological By Gilbert Meilaender ISI Books, 2000
Librarian’s tip: Chap. 7 "Cloning and Begetting"
Sacred Body? Stem Cell Research and Human Cloning By Bedford-Strohm, Heinrich The Ecumenical Review, Vol. 54, No. 3, July 2002
Human Dignity and Human Cloning By Silja Vöneky; Rüdiger Wolfrum Brill, 2004
Genes: A Philosophical Inquiry By Gordon Graham Routledge, 2002
Librarian’s tip: "Human Cloning" begins on p. 153
The National Bioethics Advisory Commission: Contributing to Public Policy By Elisha Eiseman Rand, 2003
Librarian’s tip: Chap. Three "Response to the Cloning Human Beings Report"
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