supercoiling


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supercoiling

[′sü·pər‚kȯil·iŋ]
(cell and molecular biology)
Winding of the deoxyribonucleic acid duplex on itself so that it crosses its own axis; may be in the same (positive) direction as, or opposite (negative) direction to, the turns of the double helix.
References in periodicals archive ?
As DNA undergoes transcription or replication supercoiling can occur.
At the transcription level, Fis is autoregulated, induced by high supercoiling levels, and regulated by both growth rate-dependent and stringent control systems.
impact of gyrA and parC mutations on quinolone resistance, doubling time, and supercoiling degree of Escherichia coli.
Sensitivity to the detection of single strand DNA breaks comes from the use of alkaline lysis buffer, which reverses DNA supercoiling and separates the DNA duplex into single strands.
DNA gyrase catalyses the negative supercoiling of DNA in bacteria and consists of two A subunits, encoded by gyrA, and two B subunits, encoded by gyrB.
Supercoiling can therefore be: negative (right-handed): Supercoils formed by deficit in link are called negative supercoils.
These enzymes control the degree of supercoiling and are required for undoing knots and tangles in the genetic material.
Topo II, a nuclear protein that is essential for normal cellular processes such as replication, binds to double-stranded DNA cutting it to relieve supercoiling.
Any breaks present in the DNA cause the supercoiling to relax locally, and negatively charged loops of DNA are then free to extend and migrate in the electric field toward the anode as a "comet tail.
Primarily, the quinolones act by interfering with DNA synthesis through the inhibition of DNA gyrase, which is responsible for supercoiling the DNA after replication (Mechanism A).