PCR

• The polymerase chain reaction can be usde to slect a fragment of DNA and amplify it to produce millions of copies in just a few hours.
• (1) A reaction mixture is set up that contains the DNA sample, free nucleotides, primers and DNA polymerase.

  (2) The DNA mixture is heated to 95 to break the hydrogen bonds between two strands of DNA.
• Primers are short pieces of DNA that are complementary to the bases at the start of the fragment you want.
• DNA polymerase is an enzyme that creates new DNA strands.
• DNA Polymerase doesn't denature at 95 degrees - this is important as it means many cycles of PCR can be carried out without the need of new enzymes.
• (3) The mixture is then cooled to between 50 and 65 so that the primers can bind to the strands.

  (4) The reaction mixture is heatde to 72 so DNA polymerase can work
• (5) The DNA polymerase lines up free DNA nucleotides alongside each template strand so new strands are formed.
• (6) Two new copies of the fragment of DNA are formed and one cycle of PCR is complete and the cycle starts again
• What are the temperatures in order for PCR?

  1. 95 Degrees
  2. 50 to 60 Degrees
  3. 72 Degrees
  4. 95 Degrees