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Ch20WordLectureOutline - CHAPTER 20 DNA TECHNOLOGY AND...

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CHAPTER 20 DNA TECHNOLOGY AND GENOMICS Introduction The mapping and sequencing of the human genome has been made possible by advances in DNA technology. Progress began with the development of techniques for making recombinant DNA , in which genes from two different sources - often different species - are combined in vitro into the same molecule. These methods form part of genetic engineering , the direct manipulation of genes for practical purposes. Applications include the introduction of a desired gene into the DNA of a host that will produce the desired protein. DNA technology has launched a revolution in biotechnology , the manipulation of organisms or their components to make useful products. Practices that go back centuries, such as the use of microbes to make wine and cheese and the selective breeding of livestock, are examples of biotechnology. Biotechnology based on the manipulation of DNA in vitro differs from earlier practices by enabling scientists to modify specific genes and move them between organisms as distinct as bacteria, plants, and animals. DNA technology is now applied in areas ranging from agriculture to criminal law, but its most important achievements are in basic research. A. DNA Cloning To study a particular gene, scientists needed to develop methods to isolate only the small, well-defined, portion of a chromosome containing the gene. Techniques for gene cloning enable scientists to prepare multiple identical copies of gene-sized pieces of DNA.
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1. DNA technology makes it possible to clone genes for basic research and commercial applications: an overview Most methods for cloning pieces of DNA share certain general features. For example, a foreign gene is inserted into a bacterial plasmid and this recombinant DNA molecule is returned to a bacterial cell. Every time this cell reproduces, the recombinant plasmid is replicated as well and passed on to its descendents. Under suitable conditions, the bacterial clone will make the protein encoded by the foreign gene. One basic cloning technique begins with the insertion of a foreign gene into a bacterial plasmid. The potential uses of cloned genes fall into two general categories. First, the goal may be to produce a protein product. For example, bacteria carrying the gene for human growth hormone can produce large quantities of the hormone for treating stunted growth. Alternatively, the goal may be to prepare many copies of the gene itself. This may enable scientists to determine the gene’s nucleotide sequence or provide an organism with a new metabolic capability by transferring a gene from another organism. 2. Restriction enzymes are used to make
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Ch20WordLectureOutline - CHAPTER 20 DNA TECHNOLOGY AND...

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