 The polymerase chain reaction is a process that allows individual DNA fragments to be propagated in bacteria and isolated in large amounts  The DNA polymerases used in PCR reactions are heat-stable enzymes from bacteria such as Thermus aquaticus: Taq polymerase

 First developed in mid-1980’s from an idea by Kary Mullis.  Unveiled to the public in  Gained widespread popularity in research circles by  Mullis received the Nobel Prize for Chemistry in 1993

 Primers comple- mentary to the flanking sequences of the segment of interest  Deoxynucleotide triphosphates (dNTPs).  Template DNA  Taq DNA polymerase  Buffer  A source of Mg 2+  ddH 2 O  A thermal cycler, or equivalent

 DS template DNA must be denatured at 95C  Primers hybridize, or anneal, to the template DNA  dNTPs are incorporated into the growing strand  Basically cell free DNA replication  Process of heating and cooling is repeated many times to make possibly billions of copies  Each copy serves as a template for a new strand in the next “generation”  Target DNA is amplified exponentially

 If enough of gene sequence is known, PCR provides powerful method for detecting small amounts of specific DNA molecules in a complex mixture of other molecules  Need to know enough for specific primers to be made  Used in medicine, forensic investigations, research and development, recombinant DNA techniques  PCR reactions may be easily contaminated, aseptic technique critical

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