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Gene Manipulation (Genetic Engineering) |
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Genetic engineering can be described as an in vitro manipulation of genes. It refers to artificial synthesis, modification, removal, addition and repair of the genetic material (DNA) to alter the genotype at will. It has evoked great interest because it may enable the geneticists in the near future to correct the disease-causing defective genes for the improvement of human race, and may be to even create life. |
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Recombination of DNA Technology |
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It is the most widely used technique in genetic engineering. It involves the formation of recombinant DNA and its introduction into an appropriate host. Recombinant DNA is the DNA formed by combining DNAs from different organisms. The technique requires skilful handling of genetic material and, therefore, the term genetic engineering is used to describe it. The properties of DNA which help in the formation of recombinant DNA are denaturation and renaturation. Denaturation is the separation of the two strands of DNA by breakdown of hydrogen bonds on heating. Renaturation is the reunion of the complementary strands on cooling, to form the DNA double helix. Thus, the single strands of DNA from different sources can join if these segments have complementary base pairs. |
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Tools |
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Several kinds of specific enzymes are employed in genetic engineering. These include lysing enzymes, cleaving enzymes, synthesizing enzymes, joining enzymes and alkaline phosphates. |
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Artificial Synthesis of DNA |
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In 1961, Kornberg and his coworkers synthesized DNA from a mixture of deoxyribonucleoside triphosphates, DNA polymerase enzyme, metal ions and a segment of viral DNA functioning as a primer. The synthetic DNA showed biological activity. When introduced into bacteria, this DNA coded one from which primer DNA was taken. |
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Introduction of Recombinant DNA into Host |
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Earlier E. coli was used as a host for the recombinant DNA. Now Bacillus subtilis and yeast are also being used. The bacteria to be used as hosts should be without plasmids. Their wall is made permeable by treatment with calcium chloride or lysozyme. The recombinant DNA is added to the culture in which such bacteria are growing. The recombinant DNA is taken up by bacteria along with nutrients. It replicates whenever the bacterial cell divides and may express the information of both the parent DNAs. The hybrid cells formed in the above process may be considered a new species. The technique allows the cloning of multiple copies of the desired gene. |
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Vectorless Gene Transfer |
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Electroporation: Temporary holes are formed in the plasma membrane of the host cell by applying a high voltage. These pores permit entry of foreign DNA. |
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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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Gene Cloning |
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Gene cloning refers to the production of a large population of a DNA fragment in pure form. Gene cloning involves the formation of a recombinant DNA and its introduction into an appropriate host, such as Escherichia coli or Bacillus subtilis. The host used should be without plasmids. The walls of host bacteria are made permeable by treatment with calcium chloride or a lysozyme. The recombinant DNA is added to the culture in which such host bacteria are growing. The recombinant DNA is taken up by the bacteria along with the nutrients. |
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Plant Cloning |
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Scientists have genetically engineered agronomically important crop plants, using the meristematic cells. |
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Cloning of Organisms |
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Two or more individuals with identical genetic make up formed from one parent by asexual reproduction are called clones. For example, daughter plants produced by strawberry runners and whole plants produced by tissue culture are clones. Similarly, the individuals formed by budding on the same parent Hydra are also a clone. |
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Transgenics |
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The organisms which contain functional genes which have been experimentally introduced by genetic engineering from another species are called transgenic organism or genetically modified organisms (GMOs). |
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DNA Finger Prints |
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The technique of finger printing was perfected by British genetist Dr. Alec Jeffreys in 1984. |
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Designer Plants |
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Many years ago, Frederick Steward and his co-workers cultured cells from carrot plants and induced some of them to develop into small embryos. Some of these embryos grew into whole plants. Today, researchers routinely regenerate crops, plants and many other plant species from cultured cells. They use various methods to pinpoint a gene in a culture that contains, say, millions of cells. Suppose the researcher includes a toxic product of a pathogen in the culture medium. If only a few cells carry a gene that confers resistance to the toxin, they will be the only ones surviving. |
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Genomics |
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Genomics is the study of genomes and genes based on DNA sequencing. Genome is the total gene complement of a haploid set of chromosomes and inherited as a unit from one parent. |
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Summary |
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Genetic engineering is the in vitro manipulation of genes. It refers to artificial synthesis, modification, removal, addition and repair of the DNA of an organism so that its phenotype can be desirably modified. |
