The process of reproducing a plant or animal identical to one of its kind.
The reproduction of an individual organism by asexual means.
The process of producing offspring which are genetically exactly the same as the parent, of producing clones.
Cloning, from the Greek klon meaning a cutting such as is used to propagate plants, is essentially a form of asexual reproduction. The initial stages were first successfully achieved in rabbits. In essence the technique consists of destroying the nucleus of the egg and replacing it with the nucleus from a body cell of the same species either a male or a female. This provides the egg with a full complement of chromosomes and it starts to divide and grow just as it would if it had retained its nucleus and been fertilized with a spermatozoon. The vital difference is that the embryo resulting from this cloning process owes nothing genetically to the female egg. It is identical in every respect with the animal from which the introduced nucleus was obtained.
From the Greek klon meaning “twig” or “graft,” clones are duplicates of organisms derived from a single individual. Until recently the cloning of a whole animal from a cell of an adult animal was considered to be a pseudoscientific fiction; the only scientific cloning that was possible was gene cloning, meaning the production of identical copies of a specific gene, or piece of DNA, for use in genetic engineering. The method involves inserting the piece of DNA in the form of a plasmid, a small loop of DNA, into a bacterium. When the bacteria multiply, the plasmid duplicates itself many times and so produces a large number of gene clones.
The procedure of gene cloning has been commonly used in plant breeding, with some experimentation in animals. In an experiment with frogs in the 1970s, a team led by John Gurdon at the University of Cambridge, England, transplanted nuclei from the skin cells of adult frogs into frogs’ eggs that were deprived of their own nuclei. In this experiment some embryos grew into tadpoles, but none reached adulthood.