Statement:: Topoisomerases help in relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix (Topoisomerases are enzymes that participate in the over winding or underwinding of DNA). The strain is same as caused when two ropes twisted around each other are untwisted from both ends.
As shown in the image the ropes develop supercoils on being unwound. The knots caused due to untwisting develops tension enough to make it impossible to uncoil the rope further.
My question is : What causes such unwanted stress(called torisonal stress maybe) and these knots? Why does it happen only with coiled strands of rope?
I think it is because of the shear strain caused by untwisting a rope but I cannot imagine how.
Maybe a free body diagram will help.
I believe that the reason behind this is also the answer to other similar queries that I have:
1.Why does the rope supercoil on being untwisted?
2.Why does a rope supercoil after forming a helix on twisting it for sometime?
3.Is it true that n ropes braided together give more strength than a single rope of their total length or n parallel ropes(unbraided)?
I believe that the answer to my original question will also be the answer to the other three phenomena
All research has failed at providing the right solution to this problem(or even an incentive)
Before you downvote me for multiple questions in one post,
All questions are completely related.
Also there is only one main question and others are just mentioned
Reference: https://www.physicsforums.com/threads/unwinding-strands-of-rope.1016887/
