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36 Cards in this Set
- Front
- Back
1. Semiconservative process
2. DNA polymerase(s) Components required for DNA synthesis 3. Origin of replication 4. Bi-directional 5. Replicating forks 6. Leading strand 7. Lagging strand (Okazaki fragments) |
General concepts of DNA replication
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These proteins need the following for DNA synthesis:
a. Substrates: dATP, dTTP, dCTP & dGTP b. Mg2+ c. Template d. Primer chain with free 3' hydroxyl group |
DNA polymerases
DNA polymerases can only carry out the process of elongation; they can not carry out the process of initiation. |
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The addition of a deoxyribonucleotide to the __' end of a polynucleotide chain
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3' end
The fundamental reaction by which DNA is synthesized |
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DNA synthesis occurs in the ____' to 3' direction.
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5'
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Site of unwinding of parental duplex and DNA synthesis
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Replication forks (two)
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Function:
DNA repair Replication (minor) Exonuclease activity: - 3' to 5' - 5' to 3' (exonuclease removes RNA primer.) |
Pol I
Replication is assisted by removal of RNA primers in conjunction with RNase H Fills in gaps after removal of RNA primers |
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Function:
DNA repair (Damage bypass) Exonuclease activity: - 3' to 5' |
Pol II
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Function:
DNA repair Replication (major) Exonuclease activity: - 3' to 5' |
Pol III
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Pol III holoenzyme core complex:
Polymerase |
Alpha subunit
Synthesizes DNA |
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Pol III holoenzyme core complex:
3' -> 5'exonuclease |
Epsilon subunit
Proofreads DNA |
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Pol III holoenzyme core complex:
Stimulates 3' -> 5' exonuclease |
Theta subunit
Regulates activity of epsilon |
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Pol III holoenzyme core complex:
Forms sliding clamp |
Beta subunit
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Pol III holoenzyme core complex:
Enhances dimerization of core; ATPase |
Tau subunit
Forces core to form a dimer Protein will have two active sites. |
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The number of nucleotides added before dissociation
A measure of efficiency. Pol III holoenzyme complex processivity = >500,000 nucleotides added before dissociation |
Processivity
The high processivity of Pol III is due to the Beta subunit and Gamma complex. |
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Action of helicases at the replicating fork introduces positive supercoiling ahead of the fork.
Removed through the action of DNA gyrase. |
If the positive supercoiling ahead of the fork is not removed through the action of DNA gyrase, then replication will cease.
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In the final steps of replication, the RNA primers are removed and the resulting gaps in the DNA fragments are filled in by the action of Pol ____.
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I
- Synthesizes DNA 5'-3' - Fragments not joined together Next the DNA fragments are joined together by DNA ligase |
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- Requires NAD+ in prokaryotes
- ATP in eukaryotes |
DNA ligase
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Hydrophobic interactions
Phe, Ile interact with Ile and Leu Ionic interaction Glutamate and arginine |
Forces that hold the subunits together
Gamma subunit can disrupt these bond |
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First step of DNA replication
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Binding of a DNA-A tetramer
Adds 20-40 DnaA monomers |
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Dna-___ protein regulates activity of DNA-b protein.
Cannot bind |
C
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DNA-__
Allows DNA-b to add to each end of the open complex |
T
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Unwinds ds- DNA at the forks
Requires ATP Displaces Dna-A proteins as it moves to the right. |
Dna-B protein = helicase
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Composed of three different proteins
DNA-b Primase PriA |
Primosome
- Forms at each end of open complex |
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Action of Pri __ and ___ loads Primase and PriA onto DNA complex
Forms Primosome |
B and C
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1. Substrates: ATP, GTP, CTP, UTP
2. Mg2+ 3. Template to direct process 4. No primer required. 5. Primer synthesized in 5'-3' direction |
Primase synthesizes RNA primers
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Need the RNA primer _____ time for the leading strand.
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one
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After synthesizing the primer for leading strand, the _______ strand primers will be formed.
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lagging
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Synthesizing DNA in 5'-3' direction
Need template to run 3'-5' direction Have parallel orientation of both strands can synthesize two strands at one time. |
Loop converts antiparallel orientation to parallel
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Top B subunit remains attached throughout the entire process.
What about the lower B subunit? . |
Lower B subunit has to cycle on and off as it runs out of template
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If positive supercoiling is not removed, replication wil l cease
DNA gyrase binds to this region and removes positive supercoiling. |
Major target for treating bacterial infections
Block DNA gyrase |
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This protein is used as a diagnostic marker for proliferating cells
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Proliferating cell nuclear antigen
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