clone

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. 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 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.

Population of genetically identical cells or organisms that originated from a single cell or organism by nonsexual methods. Cloning is fundamental to most living things, since the body cells of plants and animals are clones that come ultimately from a single fertilized egg. More narrowly, the term refers to an individual organism grown from a single body cell of its parent that is genetically identical to the parent. Cloning has been commonplace in horticulture since ancient times; many varieties of plants are cloned simply by obtaining cuttings of their leaves, stems, or roots and replanting them. The body cells of adult humans and other animals are routinely cultured as clones in the laboratory. Entire frogs and mice have been successfully cloned from embryonic cells. British researchers led by Ian Wilmut achieved the first success in cloning an adult mammal in 1996. Having already produced clones from sheep embryos, they were able to produce a lamb (Dolly) using DNA from an adult sheep. The practical applications of cloning are economically promising but philosophically unsettling.

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Clone may refer to:

Science

• Clone (B-cell biology), a process of immunological B-cell maturation
• Clone (genetics), in molecular biology, an exact replica of all or part of a macromolecule (e.g. DNA)
• Clone (plant), in horticulture and biology, any organism whose genetic information is identical to that of a "mother organism" from which it was created
• Clone (cell biology), a group of identical cells naturally derived from a common mother cell; of significance in vertebrate physiology, and concepts related to immunology and cancer biology

Computing

• Clone (computing), a computer made by a third party, such as PC clones or Macintosh clones.
• Clone (database), a complete and modified copy of a database environment that's often used for development or testing purposes.
• Clone (function), various functions in computer programming

Entertainment

Music

• Clone (Threshold album), a 1998 album by British progressive metal band Threshold
• Clone, a song by punk band Avail, from their 1994 album Dixie

Other

• Clone (computer and video games), a game or game franchise heavily inspired by another
• Cl.one, an independent film

Mathematics

• Clone (algebra), a collection of functions with certain properties

Other uses

• Clone (voting), in voting systems analysis, a candidate identical to one already present in an election
• Clone Wars

See also

• Clones (disambiguation)
• Cloning (disambiguation)
• Clonal