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15 Cards in this Set
- Front
- Back
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What does topoisomerase do?
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Cuts DNA strand allowing unravelling.
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What is the difference between topoisomerase I and II?
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Topo I cuts just one strand of DNA, topo two does two (they immediately repair the damage after one turn)
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Why are topoisomerase inhibitors useful as antibacterials?
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Stop the DNA from relieving unwinding strain, stop DNA copying, stop the life of the cell.
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What protein separates the DNA into separate strands?
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Helicase (AKA dnaB)
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What is SSB and what does it do?
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Single-stranded binder; prevents unwound DNA on the lagging strand from reattaching to itself (acts like a door jam).
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What does Primase (DnaG) do?
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Builds an RNA primer on lagging strands of DNA.
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What does DNA polymerase I do?
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Replaces RNA primers with DNA.
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What does DNA polymerase II do?
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Repairs nicks in the strand (where OH and P- groups aren't bound)
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What does DNA polymerase III do?
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Elongates new DNA strands.
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What is the replisome and what is it comprised of?
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The unit that replicates leading and lagging strands; helicase, Beta clamp loading unit and polymerase III.
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In bacteria systems, what is an exonuclease and what is an endonuclease?
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Exo- needs a nick at the end of a DNA strand to begin elongating.
Endo- can start in the center of a strand. |
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Explain DNA polymerase I's proofreading ability.
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Contains and exonuclease active site (shown first in diagrams). When a wrong basepair is found, polymerase I will back up one space, remove the incorrect nucleotide and replace it with the correct one.
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What kind of bond connects nucleotides?
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Phosphodiester bonds.
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Which protein completes phosphodiester bonds?
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Ligase.
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DNA is repaired three ways. Name them:
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Methylation
Base excision repair Nucleotide excision repair |
