A clone is an organism, or group of organisms derived from another organism by an asexual (nonsexual) reproductive process. A group of cells stemming from a single cell is also called a clone. Usually the members of a clone are identical in their inherited characteristics. An example of clone is identical twins, which originate from the division of a single fertilized egg. Simple organism such as protozoa's, many other algae and some yeast are also reproducing primarily by cloning.
             Through recent advances in genetic engineering, scientists can isolate an individual gene (or group of genes) from one organism and grow it in another organism belonging to a different species. The species chosen as a recipient is usually one that can reproduce asexually, such as a bacterium or yeast. Thus, it is able to produce a clone of organisms, or cells, that all contain the same foreign gene or genes. Because bacteria, yeasts, and other cultured cells multiply rapidly, these methods make possible the production of many copies of a particular gene. The copies can then be isolated and used for study (for example, to investigate the chemical nature and structure of the gene) or for medical and commercial purposes (for example, to make large quantities of a useful gene product such as insulin, interferon, and growth hormone). This technique is called cloning because it uses clones of organisms or cells. It has great economic and medical potential and is the subject of active research.
             A whole nucleus, containing an entire set of chromosomes, can be taken from a cell and injected into a fertilized egg whose own nucleus has been removed. The division of the egg brings about the division of the nucleus, and the descendant nuclei in turn, be injected into eggs. After several such transfers, the nuclei may be capable of directing the development of the eggs into complete new organisms genetically identical to the organism from which the original nucl...