The Polymerase Chain Reaction

• What is the polymerase chain reaction?

  A method of copying fragments of DNA.
• What kind of process is the polymerase chain reaction, and why is this an advantage?

  An automated process, making it rapid and efficient.
• What does the process require?

  The DNA fragments to be copied, DNA polymerase, primers, nucleotides containing the four bases in DNA, and thermocyclers.
• What are the three stages of the polymerase chain reaction?

  Seperation of the DNA strand, addition of primers, and synthesis of DNA.
• What happens during separation of the DNA strand?

  The DNA fragments, primers and DNA polymerase are placed in a vessel in the thermocycler, the temperature is increased to 95*C, causing the two strands to separate due to the breaking of hydrogen bonds between bases.
• What happens during addition (annealing) of the primers?

  The mixture is called to 55*C, causing the primers to join (anneal) to their complementary bases at the end of the DNA fragment.
• Why are primers joined to the DNA fragment?

  they provide the starting sequence for dan polymerase to begin DNA copying as it can only attach nucleotides to the end of an existing chain.
• What do the primers prevent?

  The two separate strands from rejoining.
• What happens during synthesis of DNA?

  The temperature is increased to 72*C which is the optimum temperature for DNA polymerase to add complementary nucleotides along the separate strands, starting at the primer, adding nucleotides till it reaches the end of the chain.
• What happens after the DNA strands have been synthesised?

  The process is repeated with the copied strands, resulting in four strands.