Alternative Ways for Cloning
In the media, the term "clone" often refers to individuals with the same genetic information as their parent organism--and cloning is used to mean a technique to make clones. In biology, however, the word "clone" also has other meanings.
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Types
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Gene cloning (also called molecular cloning) is a technique to isolate a gene of interest and make copies of it in bacteria. Reproductive cloning describes two techniques, somatic cell nuclear transfer (SCNT) and cloning with induced pluripotent stem cells (iPSCs), which generate clones or individuals genetically identical to the parent individual. Cloning in horticulture refers to techniques like grafting that generate genetically identical copies of a single plant. When reporters and journalists talk about cloning, they are typically referring to SCNT.
Function
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In molecular cloning, a gene is spliced into a plasmid, a small circular piece of DNA, and introduced into bacteria, which make copies of the plasmid as they divide. SCNT involves transferring DNA from an adult or somatic cell to an egg cell whose nucleus has been destroyed; the egg cell is induced to divide to form an embryo then transferred to the uterus of a female host. Alternatively, adult cells can be reprogrammed into a kind of immature unspecialized cell called a stem cell; the stem cells are then inserted into early stage embryos to produce a clone.
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Significance
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SCNT is the most common type of cloning and the method used to produce Dolly the sheep. The use of cloning for therapeutic purposes (e.g., to harvest embryonic stem cells) has been proposed as one application of the technology but remains controversial. Gene or molecular cloning, on the other hand, finds innumerable uses in biotechnology; up until the invention of an alternate method in the 1980s, it was the only reliable way to copy a DNA sequence.
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References
- Photo Credit pretty woman and her clones on meadow image by Pavel Losevsky from Fotolia.com
