Unit 1.2 - The replication of DNA

• Why is DNA a unique molecule?

  It's able to direct its own replication and produce an exact copy of itself.
• Why is the DNA's unique molecule important?

  So that each daughter cell contains the exact same genetic information as the original parent cell.
• What are the 5 requirements for DNA replication?

  1. DNA Template
  2. Enzymes
  3. Primers
  4. ATP
  5. Free DNA Nucleotides
• What is the first step of DNA Replication?

  DNA unwinds and the weak hydrogen bonds between the base-pairs break to form two template strands. The DNA becomes denatured.
• What is a primer?

  A short strand of nucleotides needed to start DNA replication.
• What is the second step of DNA replication?

  A primer binds to the 3' end of the template DNA strand, allowing DNA polymerase to add DNA nucleotides.
• What is the strand with the free 3' end called?

  The leading strand.
• What is the strand with the free 5' end called?

  The lagging strand.
• What enzymes do leading strands use?

  DNA polymerase.
• How many primers do leading strands use?

  One primer only.
• Are leading strands continuous or discontinuous?

  Continuous
• What enzymes do lagging strands use?

  DNA polymerase and ligase.
• How many primers do lagging strands use?

  Multiple primers
• Are lagging strands continuous or discontinuous?

  Discontinuous.
• What is PCR?

  Technique for the amplification of DNA
• What does PCR require?

  1. Sequence of DNA
  2. Primers
  3. DNA nucleotides
  4. Heat tolerant DNA polymerase
• What are primers in PCR?

  Short strands of nucleotides which are complementary to specific target sequences at the two ends of the region of DNA to be amplified.
• What happens in Stage 1 of PCR?

  DNA is heated to between 92-98C to break the hydrogen bonds between base pairs. This allows for the seperation of the DNA strands. The DNA becomes denatured.
• What happens during stage 2 of PCR?

  The DNA is then cooled to 50-65C to allow the primers to bind to their specific targeted sequence at the 3' ends.
• What happens during stage 3 of PCR?

  The DNA is then heated to between 70-80C for heat tolerant DNA polymerase to replicate the region of DNA.
• What is produced from PCR?

  Two identical copies of DNA.