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

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

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

4. dATP
DNA polymerase III (from E. coli)
- Enzyme responsible for almost all DNA replication
- Extends DNA polymers by adding nucleotides to 3’ ends
DNA Pol III
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. (b) Separation of strands
Fig
It looks so simple….. A T A T A T A T C G C G C G C G T A T A T A T A A T A T A T A T G C G C G C G C
(a) Parent molecule
(b) Separation of strands
(c) “Daughter” DNA molecules, each consisting of one parental strand and one new strand

9. Prokaryotic replication
Fig a
Prokaryotic replication
Origin of replication
Parental (template) strand
Daughter (new) strand
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)
Fig
DNA needs to be made single stranded (and kept that way)
Primase
Single-strand binding proteins 3’ 3
Topoisomerase 5 3
RNA primer 5 5 3
Helicase

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

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

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

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

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

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

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

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

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

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

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

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

23. Lagging strand template 3 5 DNA pol III Lagging strand 3 5
Figure 16.18
DNA pol III
Parental DNA
Leading strand 5 5 3 3 3 5 3 5
Connecting protein
Helicase
Lagging strand template 3 5
Figure A current model of the DNA replication complex.
DNA pol III
Lagging strand 3 5

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

25. 3’GACTACAGTTGACGTACG5’
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