Term
| What are the three functions of DNA polymerase I? |
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Definition
DNA Repair, removes primer
5'-3' polymerization
3'-5' exonuclease activity
5'-3' exonuclease activity (removes RNA primers) |
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Term
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Definition
| Cleave nucleotides from the end of a strand of DNA, breaking the phosphodiester bonds |
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Term
| What do endonucleases do? |
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Definition
| Cleaves phosphodiester bonds in the middle of strand of DNA |
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Term
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Definition
| an enzyme that degrades DNA |
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Term
| What are the requirements for DNA synthesis in prokaryotes? |
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Definition
-primer
-nuleotide with a free 3'OH
-all four dNTPs |
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Term
| What do topoisomerases do? What is the difference between topoisomerase I and topoisomerase II? |
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Definition
-remove the stress from supercoiling
I removes 1 supercoil at a time
II removes two supercoils at a time |
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Term
| What does DNA polymerase II do? |
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Definition
DNA repair: 5'-3' polymerization
3'-5' exonoclease |
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Term
| What does DNA polymerase III do? |
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Definition
DNA replication:
5'-3' polymerization
3'-5' polymerization |
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Term
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Definition
| joins ends of Okazaki fragments, catalyzing the formation of a phosphodiester bond between 3'OH & 5'PO4 |
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Term
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Definition
| A form of RNA primase when creates a primer for DNA replication |
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Term
| Describe the steps of DNA replication |
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Definition
1. Recognition of replication origin (oriC in E.coli)
2. Opening of DNA strand by helicase
3. Binding of single stranded binding proteins
4. Removal of positive supercoils
(topoisomerases & gyrase)
5. Priming of template (DNA primase)
6. DNA polymerization (DNA polymerases + ligases) |
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Term
| What are the four subunits of gyrase? |
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Definition
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Term
| How does DNA gyrase function? |
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Definition
| Cleaves both strands of DNA, passes one over the other and then reseals |
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Term
True or False
Gyrase is a type II topoisomerase |
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Definition
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Term
| Describe the proofreading activity of polymerase |
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Definition
| Before adding a nucleotide, polymerase proofreads and will remove any mismatched bases (3'-5' exonuclease activity) before proceeding with the 5'-3' polymerase activity |
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Term
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Definition
primase + DNA helicase
-initiates okazaki fragments on lagging strand
-unwinds DNA and synthesizes RNA primer
.....rest of steps of replication |
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Term
| What is the structure of DNA poly III? |
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Definition
| Holoenzyme + catalytic core |
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Term
| What is the holoenzyme in DNA poly III? |
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Definition
| multimeric complex of approx 20 polypeptides |
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Term
| What is the catalytic core |
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Definition
| In DNA poly III, alpha units have polymerase |
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Term
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Definition
The complete replication apparatus at replication fork
Consists of primosome + poly III holoenzyme
Lagging strand forms loop to connect to poly III core |
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