REPLICATION

• WHAT TYPE OF REPLICATION OCCURS IN DNA?

  semi-conservative replication
• WHAT DOES SEMI-CONSERVATIVE REPLICATION MEAN?

  each new DNA molecule contains one parental strand and one newly synthesised strand
• WHEN DOES DNA REPLICATION OCCUR?

  before cell divisions as all DNA must replicate for copy for new cells
• PROCESS?

  1. DNA helicase breaks hydrogen bonds between base pairs
  2. Double helix unwinds
  3. Each strand acts as a template
  4. Free DNA nucleotides attach to complimentary base pairs on templates
  5. Adjacent nucleotides joined by condensation reaction forming phosphodiester bonds
  6. DNA polymerase catalyses joining of nucleotides
  7. Two sets of daughter DNA (one parental and one newly synthesised strand)
• EVIDENCE FOR DNA REPLICATION?

  Watson and Crick

  Franklin

  Meselson and Stahl
• WHAT DID WATSON AND CRICK DISCOVER?

  structure of DNA
• WHAT DID FRANKLIN RESEARCH?

  X-ray diffusion
• WHAT DID MESELSON AND STAHL PROVE?

  DNA replication must be semi-conservative (14N and 15N)