2016年2月27日 · Supercoiling occurs when the molecule relieves the helical stress by twisting around itself. Overtwisting leads to postive supercoiling, while undertwisting leads to negative supercoiling. And finally from wikibooks: Positive and Negative Supercoilings. Positive supercoiling is the right-handed, double helical form of DNA. It is twisted tightly ...

2019年8月26日 · Supercoiling just relieves the stress introduced after DNA gets further twisted in the first place, it relaxes the DNA by decreasing the twist back to normal (10.4bp per turn just like normal relaxed B-DNA) (in case of positive sueprcoiling and vice versa for negative) and the extra tension that made the DNA twisted in the first place now ...

2017年4月1日 · In so-called "extreme" conditions (e.g. high acidity or high T˚) the organism must protect his DNA from degradation. Therefore those organisms require a more stable form of their DNA which can be achieve by positive-supercoiling and/or high GC content. Now why do the vast majority of the organisms have negatively-supercoiled DNAs?

My speculations: Underwinding cause the adjacent DNA to overwind and as the DNA overwinds the associated stress developed cause the DNA to form positive supercoils (which would have happened naturally had new twists been introduced in the DNA (Time:1:54) ).

2016年12月6日 · $\begingroup$ @BryanKrause Expecting that you are aware of DNA replication and supercoiling in general I put the issue in my words,one book says that DnaA protein forms an oligomeric complex and the DNA wraps around it in right handed fashion creating positive supercoils that denatures the weak A=T rich regions and that's where the rep. bubble is formed.

2021年7月19日 · What is positive and negative supercoiling? Is the following correct? Positive supercoiling = the coiling of DNA helix (B-DNA) on itself during intesified coiling of the two DNA stands in right handed direction negative supercoiling = the ...

2016年10月8日 · DNA supercoiling refers to the over- or under-winding of a DNA strand. Source : DNA supercoil When a relaxed DNA is subjected to bends, or openings of DNA, over winding or unwinding , its base pairs per turn changes, and the DNA is subjected to stress and strain.

2014年4月29日 · Additionally, supercoiling is present in DNA normally. Supercoiling is the result of more or less twist in a DNA helix, which is most stable when it has ~10.5 bp/turn (for B-DNA). Supercoiling allows under- or overwound DNA to return to its most stable twist. Negative supercoiling is the result of underwound DNA.

2016年10月8日 · At each replication fork, DNA helicase unwinds the DNA and topisomerase alleviates positive supercoiling. Is it proper to say that helicase "unwinds" DNA? In other places in the book, it says the function of helicase is to separate the two strands of DNA, and topoisomerase "relieves the supercoiling" caused by the strand separation activity of ...

I am currently studying the supercoiling of DNA. I understand why overwinding would create additional strain for two attached strands of DNA, but I really don't get why underwinding would create strain and thus supercoiling. If anything it seems that the strands would just separate and strain would be relieved from any DNA helix.