DNA replication

• Conditions for replication to take place

  • free nucleotides available
  • both strands acting as a template
  • enzymes DNA helicase and DNA polymerase present
  • ATP required to drive the process
• Semi-conservative replication = one original strand remains intact and a new complementary strand is formed using the old strand as a template for replication
• Process of Replication

  • DNA helicase unwinds parent DNA molecule
  • activated nucleotides attach themselves to the bases on the parent polynucleotide strands by complementary base pairing
  • new DNA molecules built up by the 4 bases
  • DNA polymerase catalyses the condensation reaction that joins adjacent nucleotides forming sugar-phosphate backbone
  • "proof reading" enzyme checks for mutations before a "winding" enzyme winds the daughter polynucleotides to form two DNA double helices
• Meselson and Stahl grew bacteria in different isotopes of nitrogen to test for the process of DNA replication