fig. 16-9-3
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Fig. 16-9-3
A T
GC
T A
TA
G C
(a) Parent molecule
A T
GC
T A
TA
G C
(c) “Daughter” DNA molecules, each consisting of one parental strand and one new strand
(b) Separation of strands
A T
GC
T A
TA
G C
A T
GC
T A
TA
G C
It looks so simple…..
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
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:1.Template strand of DNA2.“Primer” strand of DNA
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:1.Template strand of DNA2.“Primer” strand of DNA3.Deoxynucleoside triphosphates
dATP
deoxynucleotide triphosphates (dNTPs)i.e. dATP, dGTP, dCTP, dTTP
The fundamental building blocks for DNA synthesis
DNA Pol IIIDNA synthesis
DNA Pol III
Fig. 16-9-3
A T
GC
T A
TA
G C
(a) Parent molecule
A T
GC
T A
TA
G C
(c) “Daughter” DNA molecules, each consisting of one parental strand and one new strand
(b) Separation of strands
A T
GC
T A
TA
G C
A T
GC
T A
TA
G C
It looks so simple…..
Fig. 16-12a
Origin of replication Parental (template) strand
Daughter (new) strand
Replication fork
Replication bubbleDouble-stranded DNA molecule
Two daughter DNA molecules
(a) Origins of replication in E. coli
0.5 µm
Prokaryotic replication
Fig. 16-13
Topoisomerase
Helicase
PrimaseSingle-strand binding proteins
RNA primer
55
5 3
3
3
3’
DNA needs to be made single stranded (and kept that way)
Fig. 16-13
Topoisomerase
Helicase
PrimaseSingle-strand binding proteins
RNA primer
55
5 3
3
3
DNA synthesis is initiated by Primase making a short RNA “primer”
Fig. 16-15b
Origin of replication
RNA primer
“Sliding clamp”
DNA pol IIIParental DNA
3
5
5
5
5
5
5
3
3
3
Fig. 16-12a
Origin of replication Parental (template) strand
Daughter (new) strand
Replication fork
Replication bubbleDouble-stranded DNA molecule
Two daughter DNA molecules
(a) Origins of replication in E. coli
0.5 µm
Prokaryotic replication
Fig. 16-15a
Overview
Leading strand
Leading strandLagging strand
Lagging strand
Origin of replication
Primer
Overall directions of replication
Fig. 16-16a
Overview
Origin of replication
Leading strand
Leading strand
Lagging strand
Lagging strand
Overall directions of replication
12
Fig. 16-16b1
Template strand
5
53
3
Primase
Fig. 16-16b2
Template strand
5
53
3
RNA primer 3 5
5
3
1
Primase
DNA Pol III + S. clamp
Fig. 16-16b3
Template strand
5
53
3
RNA primer 3 5
5
3
1
13
35
5
Okazaki fragment
Primase
DNA Pol III + S. clamp
Fig. 16-16b4
Template strand
5
53
3
RNA primer 3 5
5
3
1
13
35
5
Okazaki fragment
12
3
3
5
5
Primase
DNA Pol III + S. clamp
Fig. 16-16b5
Template strand
5
53
3
RNA primer 3 5
5
3
1
13
35
5
Okazaki fragment
12
3
3
5
5
12
3
3
5
5
Primase
DNA Pol III + S. clamp
DNA Pol I
Fig. 16-16b6
Template strand
5
53
3
RNA primer 3 5
5
3
1
13
35
5
Okazaki fragment
12
3
3
5
5
12
3
3
5
5
12
5
5
3
3
Overall direction of replication
Primase
DNA Pol I
DNA Ligase
Fig. 16-17
OverviewOrigin of replication
Leading strand
Leading strand
Lagging strand
Lagging strandOverall directions of
replication
Leading strand
Lagging strand
Helicase
Parental DNA
DNA pol III
Primer Primase
DNA ligase
DNA pol III
DNA pol I
Single-strand binding protein
5
3
5
5
5
5
3
3
3
313 2
4
Figure 16.18
Parental DNA
DNA pol III
Leading strand
Connectingprotein
Helicase
Lagging strandDNA pol III
Laggingstrandtemplate
5
5
5
5
5
5
3 3
33
3
3
5’ ATGTCAAC 3’3’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?
In a test tube:DNA Pol III +
dNTPs +
deoxynucleotide triphosphates (dNTPs)i.e. dATP, dGTP, dCTP, dTTP
The fundamental building blocks for DNA synthesis
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