GMan Chp15 - Replication initiation

  1. Exception to Watson and Crick's semiconservative replication?
    Displacement replication
  2. Where does displacement replication occur?
    • Small, circular genomes
    • Animal mtDNA and phages (lambda)
  3. D-Loop
    Site where dsDNA is interrupted by a primer (between the strands)
  4. Which strand is copied first in displacement replication?
    The displaced one
  5. Types of displacement replication
    • D-Loop
    • Rolling circle
  6. How does rolling circle replication begin?
    A single strand is nicked
  7. Rolling circle replication
    • Take a good look at this
    • Image Upload 1
  8. Advantages of rolling circle replication
    Multiple copies produced rapidly
  9. (continuous of discontinuous)
    DNA synthesis is _____ at the 5' end
    DNA synthesis is _____ at the 3 end
    DNA synthesis is continuous at the 5' endDNA synthesis is discontinuous at the 3 end using RNA primers
  10. Stages of DNA replication
    Initiation, Elongation, Termination
  11. Where does DNA replication begin?
    Origin(s) of replication
  12. Replication bubble
    Separated DNA strands in DNA replication
  13. Overall DNA replication is ____
    What direction?
  14. Replication fork
    • Y-shaped region where new DNA strands are elongating
    • Point where DNA strands separate to form a replication bubble
  15. Helicases
    Melt the dsDNA at the replication fork
  16. Single stranded binding proteins
    Bind and stabilize the ssDNA
  17. Topoisomerases
    Ease tension ahead of the replication fork(s) by introducing nicks
  18. Primase
    Introduces the RNA primer used to initiate DNA synthesis
  19. Origin of replication in e.coli
    • OriC
    • ~245 Bp long
  20. Structure of OriC
    • ~245 Bp
    • Two short repeating motifs:
    • i. 9nt segments (DnaA binding)
    • ii. 13nt segments (Zone of melting)
  21. DnA A binding to OriC
    • The DnaA complex interacts with the 9nt repeats of OriC
    • This interaction causes the 13nt (AT) regions (ATP Hydrolysis) to denature (melt)
    • SSBs and DnaB are introduced
  22. Structure of the OriC 13nt nucleotides
    • AT Rich
    • Fewer hydrogen bonds make easier melting
  23. How does DnaB bind
    • Initially attached to DnaC
    • Binds melted 13nt (AT) regions along with SSBs
    • DnaC is released
  24. Structure of DnaA
    30 Monomer subunits
  25. How many DnaB/DnaB complexes load onto the replication bubble?
  26. Why is dnaC important?
    Aids proper loading of DnaB
  27. What is the helicase in the prepriming complex?
  28. How do SSBS stabillize ssDNA
    • Prevent re annealing of melted DNA (by DnaB)
    • Protect against nuclease activity
  29. Steps of initiation that use ATP
    • Melting 13nt (AT) regions after DnaA binding
    • DnaB/DnaC binding
  30. Structure of SSBs
    • Homotetramers
    • Bind to DNA in a series
  31. Conversion from Prepriming to Priming complex
    • DnaB (DNA Helicase) recruits the primase
    • Primer synthesis occurs
  32. β-subunit clamp
    • Loads after the primer is created
    • Preceeds DNA Pol III loading and elongation
Card Set
GMan Chp15 - Replication initiation