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| Cloning of Cells |
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| A population of identical molecules (genes), cells or organisms, all of which are derived from the same parent by asexual means, is known as a clone1. The process of producing genetically similar molecules, cells, or organisms from a common precursor by asexual reproduction in vitro or in vivo is termed cloning. (“in vitro in Latin means “in glass”). |
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| Different techniques are used for cloning genes, cells and organisms. |
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| Genetically altered or modified microbial cells can be duplicated very easily and we can get millions of cloned cells in a few days. These microbial strains are used for a number of purposes. |
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| a. To produce useful compounds such as enzymes and vitamins on large scale. |
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| b. They can be engineered to produce pharmaceutically useful products like human insulin, interferon, human growth hormone and viral vaccines example: E. coli. |
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| fig. 25.4 - Mechanism of transferring insulin gene from rat DNA to E. coli with a Plasmid |
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| c. Several microbial strains are being used in the industries for performing various functions like the removal of undesired lignin. Example Trametes. |
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| d. Microbes like Pseudomonas can also be used to purify polluted environment. This is termed as bioremediation. |
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| e. Certain microbes like Trichoderma and Rhizobium against plant diseases and pests and as bio fertilisers. |
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| In this technique an animal tissue is broken into separate cells by mechanical agitation or by immersing in a mixture of (a) proteases, such as trypsin and collaginase, and (b) calcium-binding agents. The proteases break down the extra cellular materials that bind the cells together. The calcium-binding agents remove calcium ions required for adhesion between cells. This procedure gives a cell suspension containing different types of cells. |
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| A small number of cells are added to a glass dish and covered with a nutrient medium. The latter provides (i) the optimum environment such as pH, osmotic pressure, etc.; and (ii) the chemical materials that the cells cannot synthesize. The nutrient medium may be natural (serum, chick embryo extract; liver extract) or artificial (solution containing salts, amino acids, vitamins, carbohydrates, etc.). The cells often adhere to the bottom of the dish, a little distance away from each other. The isolated cells proliferate and produce distinct colonies or clones of identical cells, in about 7-10 days. All these cells in a clone are derived from a single parent cell by mitotic divisions. The clones may be isolated and propagated. |
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| Most micro-organisms, both prokaryotic and eukaryotic, which live in nature as single cells, can be easily cloned in vitro, using agar as a nutrient medium. |
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| fig. 25.5 A Clone Named Dolly of a Sheep |
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| fig. 25.6 Cloning of a Sheep |
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