Cloning is the process of ‘deriving’ an organism or a group of cells from another organism or from a single cell asexually. Members of a clone are identical in their inherited characteristic that is, in these genes except for any differences caused by mutation. Identical twins who originate by the division of a single fertilized egg are members of a clone, whereas non identical twins that derive from two separate fertilized eggs are not, according to the Encyclopedia.
Through recent advances of genetic engineering, scientists can isolate one or more 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 of cell, that all contain the same foreign gene or genes. They make many copies of a particular gene.
The copies can then be isolated and used to study. As this procedure involves clones of organisms or cells it is called cloning.
Identical twin animals can also be produced by cloning. An embryo in the early stage or development is removed from the uterus and split, and then each separate part is placed in a surrogate uterus. This method has been used to produce mice and sheep.
Another development has been the discovery that 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 can, in their turn, be injected into eggs.
After several such transfers, the nuclei may become capable of directing the development of eggs into complete new organisms genetically identical to the organism from which the original nucleus was taken. This cloning technique is thus, capable of producing large numbers of genetically identical individuals. Such experiments have been carried out with frogs, mice and now with sheep and monkey.
