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Fig. 16-9-3

It looks so simple…. A. T. A. T. A. T. A. T. C. G. C. G. C. G. C. G. Fig. 16-9-3. A. T. A. T. A. A. T. T. T. A. T. A. T. T. A. A. C. C. G. C. G. C. G. G. (c) “Daughter” DNA molecules, each consisting of one parental strand and one new strand.

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Fig. 16-9-3

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  1. It looks so simple….. A T A T A T A T C G C G C G C G Fig. 16-9-3 A T A T A A T T T A T A T T A A C C G C G C G G (c) “Daughter” DNA molecules, each consisting of one parental strand and one new strand (b) Separation of strands (a) Parent molecule

  2. DNA Pol III DNA polymerase III (from E. coli) - Enzyme responsible for almost all DNA replication - Extends DNA polymers by adding nucleotides to 3’ ends

  3. DNA Pol III DNA polymerase III (from E. coli) - Enzyme responsible for almost all DNA replication - Extends DNA polymers by adding nucleotides to 3’ ends • Requires: • Template strand of DNA • “Primer” strand of DNA

  4. dATP DNA Pol III DNA polymerase III (from E. coli) - Enzyme responsible for almost all DNA replication - Extends DNA polymers by adding nucleotides to 3’ ends • Requires: • Template strand of DNA • “Primer” strand of DNA • Deoxynucleoside triphosphates

  5. deoxynucleotide triphosphates (dNTPs) i.e. dATP, dGTP, dCTP, dTTP The fundamental building blocks for DNA synthesis

  6. DNA synthesis DNA Pol III

  7. DNA Pol III

  8. It looks so simple….. A T A T A T A T C G C G C G C G Fig. 16-9-3 A T A T A A T T T A T A T T A A C C G C G C G G (c) “Daughter” DNA molecules, each consisting of one parental strand and one new strand (b) Separation of strands (a) Parent molecule

  9. Prokaryotic replication Origin of replication Parental (template) strand Daughter (new) strand Fig. 16-12a Replication fork Double-stranded DNA molecule Replication bubble 0.5 µm Two daughter DNA molecules (a) Origins of replication in E. coli

  10. DNA needs to be made single stranded (and kept that way) Primase Single-strand binding proteins 3’ Fig. 16-13 3 Topoisomerase 5 3 RNA primer 5 5 3 Helicase

  11. DNA synthesis is initiated by Primase making a short RNA “primer” Primase Single-strand binding proteins Fig. 16-13 3 Topoisomerase 5 3 RNA primer 5 5 3 Helicase

  12. Origin of replication 3 5 RNA primer 5 Fig. 16-15b “Sliding clamp” 3 5 DNA pol III Parental DNA 3 5 5 3 5

  13. Prokaryotic replication Origin of replication Parental (template) strand Daughter (new) strand Fig. 16-12a Replication fork Double-stranded DNA molecule Replication bubble 0.5 µm Two daughter DNA molecules (a) Origins of replication in E. coli

  14. Overview Origin of replication Fig. 16-15a Leading strand Lagging strand Primer Leading strand Lagging strand Overall directions of replication

  15. Overview Origin of replication Fig. 16-16a Leading strand Lagging strand Lagging strand 2 1 Leading strand Overall directions of replication

  16. Primase 3 5 3 5 Template strand Fig. 16-16b1

  17. Primase 3 5 3 5 Template strand DNA Pol III + S. clamp 3 5 3 RNA primer 1 5 Fig. 16-16b2

  18. Primase 3 5 3 5 Template strand DNA Pol III + S. clamp 3 5 3 RNA primer 1 5 Fig. 16-16b3 3 Okazaki fragment 5 3 1 5

  19. Primase 3 5 3 5 Template strand DNA Pol III + S. clamp 3 5 3 RNA primer 1 5 Fig. 16-16b4 3 Okazaki fragment 5 3 1 5 3 5 3 2 5 1

  20. Primase 3 5 3 5 Template strand DNA Pol III + S. clamp 3 5 3 RNA primer 1 5 Fig. 16-16b5 3 Okazaki fragment 5 3 1 5 3 5 3 2 5 1 5 3 3 5 1 2 DNA Pol I

  21. Primase 3 5 3 5 Template strand 3 5 3 RNA primer 1 5 Fig. 16-16b6 3 Okazaki fragment 5 3 1 5 3 5 3 2 5 1 5 3 3 5 1 2 5 3 DNA Pol I 3 5 1 2 DNA Ligase Overall direction of replication

  22. Overview Origin of replication Lagging strand Leading strand Fig. 16-17 Leading strand Lagging strand Single-strand binding protein Overall directions of replication Helicase Leading strand 5 DNA pol III 3 3 Primer Primase 5 3 Parental DNA Lagging strand DNA pol III 5 DNA pol I DNA ligase 4 3 5 3 2 1 3 5

  23. Figure 16.18 DNA pol III Leading strand Parental DNA 5 5 3 3 3 5 3 5 Connectingprotein Helicase Laggingstrandtemplate 3 5 DNA pol III Lagging strand 3 5

  24. In a test tube: DNA Pol III + dNTPs + 5’ ATGTCAAC 3’ 3’GACTACAGTTGACGTACG5’

  25. In a test tube: DNA Pol III + dNTPs + 5’ ATGTCAACTGCATGC3’ 3’GACTACAGTTGACGTACG5’ Why can’t dNTPs add to the 5’ end of the primer?

  26. deoxynucleotide triphosphates (dNTPs) i.e. dATP, dGTP, dCTP, dTTP The fundamental building blocks for DNA synthesis

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