PCR

• Once DNA fragments have been isolated, an automated machine can be used for the polymerase chain reaction (PCR) in order to amplify DNA.
• PCR requires a thermocycler (PCR repeats until required number of DNA), DNA fragment, DNA polymerase (taq polymerase - higher optimum temperature), primers (short single stranded sequence) and DNA nucleotides.
• PCR Method


  1 - temperature increased to 95°C to break hydrogen bonds splitting the two strands (denaturing DNA)

  2 - temperature then decreased to 55°C so primers can attach (annealing, hydrogen bonds can reform)

  3 - temperature increased to 72°C (optimum temperature of taq polymerase) and DNA polymerase attaches to complementary free nucleotides making a new strand align next to each template.
• Advantages of PCR


  1 - automated (more efficient)

  2 - rapid (100 billion copies in a few hours)

  3 - does not require living cells (quicker and less complex than in vivo)