7.5 DNA Replication

• DNA Helicase Action


  • DNA helicase unwinds the double helix

  • Creates a replication fork
• Single-Strand Binding Proteins


  • Attach to the separated strand
  • Keep them from re-annealing
• Primase Activity


  • Synthesizes short RNA primers
  • Provides a starting point for DNA synthesis.
• Leading Strand Synthesis


  • NA polymerase III adds nucleotides continuously
  • Proceeds in the 5' to 3' direction
• Lagging Strand Synthesis


  • DNA polymerase III adds nucleotides discontinuously
  • Creates Okazaki fragments in the 5' to 3' direction
• Primer Removal and Gap Filling


  • DNA polymerase I removes RNA primers
  • Fills gaps between Okazaki fragments
• Fragment Joining

  • DNA ligase joins the Okazaki fragments
  • Creates a continuous DNA strand
• Proofreading and Error Correction


  • DNA polymerases check for and correct errors
  • Ensures high fidelity of replication
• semiconservative replication


  • This process results in two identical DNA molecules, each containing one original strand and one newly synthesized strand
• DNA helicase


  • Unwinds the double helix and creates a replication fork
• DNA polymerase III


  • The main enzyme that synthesizes new DNA strands
• Primase


  • Synthesizes short RNA primers to provide a starting point for DNA synthesis
• DNA polymerase I


  • Removes RNA primers and fills gaps between Okazaki fragments
• DNA ligase


  • Joins Okazaki fragments to create a continuous DNA strand