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resistance genes and resistance can evolve quickly in populations. The E. coli that we will be using in lab have been modified so that they are incapable of conjugation or transformation (transduction is not an issue because there are no bacteriaphages in the system). The maintenance of these plasmids takes energy. In the absence of antibiotics, the bacteria may lose the plasmid that carries the resistance genes and the bacterium will become sensitive to the antibiotic. D. Polymerase Chain Reaction (PCR) Fundamentals The PCR technique is used in many areas of basic and applied sciences. The technique relies on the action of a DNA polymerase (an enzyme that can form polymers of DNA from monomeric nucleotides) to amplify large amounts of specific regions of DNA. There are many different types of DNA polymerases, and PCR uses one that has evolved in thermophilic (heat‐loving) bacteria. The extreme temperatures under which these bacteria live (sometimes exceeding 100° C) means their proteins (including enzymes) must function in conditions that would denature (inactivate) proteins derived from organisms that have evolved and are adapted to live at lower temperatures. The DNA polymerase from Thermus aquaticus is most often used in the PCR technique and it is commonly referred to as Taq polymerase, or simply Taq. The thermoresistant nature of Taq allows it to function under repetitive heating and cooling cycles, and this attribute, together with the ability of the enzyme to add monomeric nucleotides to the 3’ end of a growing strand of D...
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- Fall '11