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Gene cloning (from Greek klon, ‘twig’ or ‘graft’) involves the production of many identical copies of a given gene or piece of DNA for use in genetic engineering. This is generally achieved by inserting the original DNA, often derived from a DNA ‘library’, into bacterium in the form of a plasmid (a small loop of DNA). The bacteria multiply and the plasmid duplicates itself many times, to produce a large number of gene clones contained within the daughter cells of the original bacterium. A DNA library is a collection of cloned fragments of DNA produced by digestion of the DNA of a specific organism using a restriction enzyme. The concept of cloning is often extended to whole organisms, though these are chiefly single-celled organisms or certain plants. In this context the term clone refers to all cells derived from a chosen parent; in cells which reproduce by binary fission, the genes carried by all the cells in a clone are the same, if the appearance of mutations is discounted. Since all the cells of an organism bear the entire gene complement, it is theoretically possible to produce a completely new individual from a single, non-germ line cell. This can be done with some plants and animals such as amphibians, but the cloning of humans remains firmly in the realm of science fiction. RB
See also immunology.Further reading Zsolt Harsanyi, Genetic Prophesy Beyond the Double Helix. |
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