Chapter 20 Biotechnology

Chapter 20 Biotechnology - Chapter 20 iotechnology...

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Unformatted text preview: Chapter 20 iotechnology Overview: The DNA Toolbox Sequencing of the human genome was completed by 2007 DNA sequencing has depended on advances in technology, starting with making recombinant DNA In recombinant DNA , nucleotide sequences from two different sources, often two species, are combined in vitro into the same DNA molecule Methods for making recombinant DNA are central to genetic engineering , the direct manipulation of genes for practical purposes DNA technology has revolutionized biotechnology , the manipulation of organisms or their genetic components to make useful products An example of DNA technology is the microarray, a measurement of gene expression of thousands of different genes Concept 20.1: DNA cloning yields multiple copies of a gene or other DNA segment To work directly with specific genes, scientists prepare gene-sized pieces of DNA in identical copies, a process called DNA cloning Most methods for cloning pieces of DNA in the laboratory share general features, such as the use of bacteria and their plasmids Plasmids are small circular DNA molecules that replicate separately from the bacterial chromosome Cloned genes are useful for making copies of a particular gene and producing a protein product Gene cloning involves using bacteria to make multiple copies of a gene Foreign DNA is inserted into a plasmid, and the recombinant plasmid is inserted into a bacterial cell Reproduction in the bacterial cell results in cloning of the plasmid including the foreign DNA This results in the production of multiple copies of a single gene Using Restriction Enzymes to Make Recombinant DNA Bacterial restriction enzymes cut DNA molecules at specific DNA sequences called restriction sites A restriction enzyme usually makes many cuts, yielding restriction fragments The most useful restriction enzymes cut DNA in a staggered way, producing fragments with “ sticky ends ” that bond with complementary sticky ends of other fragments DNA ligase is an enzyme that seals the bonds between restriction fragments Cloning a Eukaryotic Gene in a Bacterial Plasmid In gene cloning, the original plasmid is called a cloning vector A cloning vector is a DNA molecule that can carry foreign DNA into a host cell and replicate there Producing Clones of Cells Carrying Recombinant Plasmids Several steps are required to clone the hummingbird β-globin gene in a bacterial plasmid: The hummingbird genomic DNA and a bacterial plasmid are isolated Both are digested with the same restriction enzyme The fragments are mixed, and DNA ligase is added to bond the fragment sticky ends Some recombinant plasmids now contain hummingbird DNA The DNA mixture is added to bacteria that have been genetically engineered to accept it The bacteria are plated on a type of agar that selects for the bacteria with recombinant plasmids This results in the cloning of many hummingbird DNA fragments, including the β-globin gene Storing Cloned Genes in DNA Libraries...
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This note was uploaded on 01/06/2012 for the course BIO 1406 taught by Professor Bethanypereira during the Fall '10 term at Collins.

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Chapter 20 Biotechnology - Chapter 20 iotechnology...

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