clone

noun

(Gr. klon: shoot) A group of cells, an organism, or a population of organisms arising from a single ancestral cell. All members of a particular clone are genetically identical. In nature clones are produced by asexual reproduction, for example by the formation of bulbs and tubers in plants or by parthenogenesis in certain animals. New techniques of cell manipulation and tissue culture have enabled the cloning of many plants and some animals. A wide range of commercially important plant species, including potatoes, tulips, and certain forest trees, are now cloned by micropropagation, resulting in more uniform crops. Cloning in animals is more complex, but has been accomplished successfully in sheep and cattle. The first mammal ever to be cloned experimentally from the body cell of an adult was a sheep ('Dolly') born in 1997 after over 200 previous failed attempts. The nucleus containing DNA was extracted from an udder cell (which had been deprived of nutrients) and inserted into an 'empty' egg cell (from which the nucleus had been removed). This reconstituted egg cell was then stimulated to divide by an electric shock and implanted into the uterus of a surrogate mother ewe, who subsequently gave birth to a clone of the original sheep. This breakthrough offers the prospect of producing exact replicas of animals with certain genetically engineered traits, for example to manufacture drugs in their milk or provide organs for human transplantation. A group of plants all originating by vegetative propagation from a single plant, and therefore genetically identical to it and to one another. The aggregate of the asexually produced progeny of an individual; also: a group of replicas of all or part of a macromolecule (as DNA or an antibody); an individual grown from a single somatic cell of its parent and genetically identical to it.