Cloning Genes
Gene cloning, or molecular cloning, has several different meanings to a molecular biologist. A clone is an exact copy, or replica, of something. In the literal sense, cloning a gene means to make many exact copies of a segment of a DNA molecule that encodes a gene. This is in marked contrast to cloning an entire organism—regenerating a genetically identical copy of the organism—which is technically much more difficult (with animals) and can involve ethical ramifications not associated with gene cloning. Molecular biologists exploit the replicative ability of cultured cells to clone genes.
Purposes of Gene Cloning
To study genes in the laboratory, it is necessary to have many copies on hand to use as samples for different experiments. Such experiments include Southern or Northern blots, in which genes labeled with radioactive or fluorescent chemicals are used as probes for detecting specific genes that may be present in complex mixtures of DNA.
Cloned genes also make it easier to study the proteins they encode. Because the genetic code of bacteria is identical to that of eukaryotes, a cloned animal or plant gene that has been introduced into a bacterium can often direct the bacterium to produce its protein product, which can then be purified and used for biochemical experimentation.
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