DNA Gyrase Role?

[justadream]

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TBR: DNA Gyrase Role



TBR says “DNA gyrases are involved in nicking and reattaching DNA so it does not tangle.”



I thought DNA gyrase wound up DNA. Is nicking/reattaching part of that?

 

[sillyjoe]

TBR: DNA Gyrase Role



TBR says “DNA gyrases are involved in nicking and reattaching DNA so it does not tangle.”



I thought DNA gyrase wound up DNA. Is nicking/reattaching part of that?

It is hard to visualize, but in the process of DNA replication there is strain placed on the double helix when unwinding it. DNA gyrase makes key nicks in DNA to relieve the stress/strain. There is more than one form of DNA gyrase, but all you need to know for the MCAT is that it stabilizes the DNA strands during unwinding/replication.

 

[Czarcasm]

TBR: DNA Gyrase Role



TBR says “DNA gyrases are involved in nicking and reattaching DNA so it does not tangle.”



I thought DNA gyrase wound up DNA. Is nicking/reattaching part of that?

The analogy given in traditional biology courses is a twisted rope. If you pull the rope in between, both ends will become even tighter. But, if you were to cut one (or both) of the two rope strands near the tightened region, untwist it, and somehow reattach it back, it would reduce the tension in the string.

 

[torontopharm]

Gyrase is there to relieve strain ahead of the replication fork by "under"-winding the DNA.
It'll basically make a break in one of the strands and then pass the other strand over it and then reseal it. It's kind of hard to picture it. You could probably Youtube some videos on topoisomerase to get a better picture.