Dictionary » S » Supercoiling



(Science: molecular biology) In circular DNA or closed loops of dNA, twisting of the DNA about its own axis changes the number of turns of the double helix.

If twisting is in the opposite direction to the turns of the double helix, i.e. Anticlockwise, the dNA strands will either have to unwind or the whole structure will twist or supercoil termed negative supercoiling.

If twisting is in the same direction as the helix, clockwise, which winds the dNA up more tightly, positive supercoiling is generated. DNA that shows no supercoiling is said to be relaxed

Supercoiling in circular DNA can be detected by electrophoresis because supercoiled dNA migrates faster than relaxed DNA. Circular DNA is commonly negatively supercoiled and the DNA of eukaryotes largely exists as supercoils associated with protein in the nucleosome. The degree of supercoiling can be altered by topoisomerases.

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Re: Experimental evidence for evolution

... introduction, including: higher growth rates on glucose, shorter lag phases, reduced peak population densities, larger average size, increased DNA supercoiling, defects in DNA repair, and changes in many gene-expression profiles. In fact, there are more than a dozen papers previously published ...

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by robsabba
Mon Jun 21, 2010 4:20 pm
Forum: Evolution
Topic: Experimental evidence for evolution
Replies: 103
Views: 195368

Why does negative supercoiling favor unwinding?

Hi, I was just studying about RNA polymerase and am a little bit confused because of this: "Negative supercoiling of circular DNA favors the transcription of genes because it facilitates unwinding." Why does negative supercoiling favor unwinding? Please help me Thank ...

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by SoyeongPark
Sat Mar 13, 2010 10:23 am
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Topic: Why does negative supercoiling favor unwinding?
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... chromatin rather than bundled into a chromosome at that point. Then, what you see is replication (which in real life would then be followed by the supercoiling into Chromosomes during Prophase), which gives the well-known X shape of the chromosome (it is actually two copies of the same chromosome ...

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by mamoru
Tue Feb 23, 2010 12:33 am
Forum: Genetics
Topic: Do Chromosomes dissolve and disappear?
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Views: 4413

DNA plasmid lab

It's all circle, just the level of supercoiling differs ;)

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by JackBean
Sat Oct 17, 2009 12:45 am
Forum: Cell Biology
Topic: DNA plasmid lab
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Re: DNA Supercoiling

So... increasing the agarose concentration makes it harder for the DNA to travel through the gel. So then, its obviously D. Thanks. I appreciate the help.

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by Onlygoodinmath
Fri Oct 09, 2009 3:20 am
Forum: Genetics
Topic: DNA Supercoiling
Replies: 3
Views: 2312
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