DNA replication

• What is the transforming principle

  DNA
• What is the distance between nucleotides

  0.34 nm
• What is the width of DNA

  2 nm
• What is the distance of 1 DNA turn

  3.4 nm
• What is the distance of 1 nucleotide

  2 nm
• How many nucleotide pairs are in each DNA turn

  10
• What are the features of DNA synthesis

  
  

  1. DNA polymerase synthesises DNA in 5' to 3' direction

  2. Proof-reading ability
• What are the requirements for DNA polymerase

  Single-stranded template DNA, dNTPs, Free 3' hydroxyl
• Why are primers required

  Create a free 3 ' Hydroxyl group for DNA polymerase to add nucleotides to
• Briefly describe semi-conservative replication

  • DNA helicase breaks hydrogen bonds
  • DNA polymerase produces complementary strand
  • DNA ligase seals nucleotides
• What does DNA helicase do

  Breaks hydrogen bonds to unwind DNA helix.
• What do single-stranded binding proteins do

  Hold the helix open
• What does primase do

  Synthesises RNA primers to initate DNA synthesis
• What does DNA polymerase III do

  Extends the DNA from the 3 ' using primers.
• What does DNA Polymerase I do

  Removes primers and fills in the gaps between the ozaki fragments
• What are Ozaki fragments

  Fragments of DNA which are synthesised discontinuously on the lagging strand
• Which strand is synthesised continously

  Leading
• Which strand is synthesised discontinously

  Lagging
• What does DNA ligase do

  Seals gaps between Ozaki fragments
• Describe the synthesis of the leading strand

  1. DNA helicase unwinds DNA
  2. Primase attaches RNA primers
  3. DNA polymerase III attaches nucleotides
• What is this diagram showing

  A replication fork.

  A) Leading strand

  B) Lagging strand

  C) Ozaki fragments

  D) Origin of replication

  
• What is this diagram showing

  Replication bubble.

  A) Origin of replication

  B) DNA ligase

  C) Leading strand

  D) Leading strand

  E) Leading strand

  F) Lagging strand

  
• Describe the proof-reading ability of DNA replication

  DNA polymerase removes the incorrectly placed nucleotides.
• Describe the synthesis of the lagging strand


  1. DNA helicase unwinds DNA
  2. Primase binds RNA primers
  3. DNA polymerase III synthesises Ozaki fragments
  4. DNA polymerase I removes primers and fills in gaps between fragments
  5. DNA ligase joins fragments together