1. DNA replication
    Is done with a system of enzymes.
  2. 1. Helicase
    • Binds to the origin breaks the hydrogen bond and unwinds the double helix.
    • This creates a replication fork.
    • DNA replication is going in both directions toward the replication fork.
  3. 2. Topoimerase
    Every time there is supercoiling it makes a cut in the DNA to relieve supercoiling and it will ligate (rejoin) the two ends back together.
  4. 3. Single Stranded Binding Proteins
    Stops hydrogen bonding to keep the DNA apart.
  5. 4. Primase
    Makes short segments of RNA primer so DNA Polymerase III can start.
  6. 5. DNA polymerase III
    Will make the new strand of DNA going 5' to 3' only.
  7. 6. DNA polymerase I
    Cuts out the primer and fills in the gap with DNA.
  8. 7. DNA polymerase II
    Has no known function.
  9. 8. DNA Ligase
    Joins the two strand together.
  10. DNA synthesis
    Is always towards the replication fork.
  11. The Leading Strand
    Can be synthesized continuously in 5' to 3' direction.
  12. The Lagging Strand
    • The direction is 3' to 5' so it cannot be synthesized continuously.
    • It's synthesized in short segments 5' to 3' called Okazaki Fragments.
    • The lagging strand is completed when an enzyme, DNA ligase fills in the spaces betweek Okazaki fragments with the correct nucleotides.
Card Set
The enzymes. The leading strand and lagging strand