What are supercoiling and topoisomerases?
In bacterial, circular DNA, as the DNA is being replicated or transcribed, the DNA is moved to compensate for the immobility of the enzymes DNA polymerase and RNA polymerase. When is moves through the polymerase, it twists. Supercoiling can be a problem because DNA can become so supercoiled that the enzyme cannot move along DNA. There are enzymes called topoisomerases, which can grab DNA, either one or both strands, cut DNA, untwist it, put it back together.