Download DNA replication

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