More recent studies of yeast rRNA synthesis suggest distinct roles of Top II and Top I, acting, respectively, to relieve positive supercoiling
ahead of and negative supercoiling
behind the advancing polymerase .
[IC.sup.50] is defined as the fluoroquinolone concentration that inhibits 50% of the supercoiling
activity of gyrase in a standard gyrase reaction.
As DNA undergoes transcription or replication supercoiling
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.
" is an abstract mathematical property, and represents the sum of what are termed "twist" and "writhe".
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
. The enzyme also reanneals the DNA to return it to normal structure and function.
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."
When so much of what goes on in our schools is mandated from afar (and often by noneducators, who know as much about the teaching/learning process as educators do about DNA supercoiling
), there is a real risk that the nation's teaching force will be de- skilled, reduced to technicians who need only carry out the plans that others have made.