Editing Writhe (section)

== Applications in DNA topology ==
[[DNA]] will coil when twisted, just like a rubber hose or a rope will, and that is why biomathematicians use the quantity of ''writhe'' to describe the amount a piece of DNA is deformed as a result of this torsional stress. In general, this phenomenon of forming coils due to writhe is referred to as [[DNA supercoiling]] and is quite commonplace, and in fact in most organisms DNA is negatively supercoiled.<ref name=bates_dnatopology_2005 />

Any elastic rod, not just DNA, relieves torsional stress by coiling, an action which simultaneously untwists and bends the rod. F. Brock Fuller shows mathematically<ref name=fuller_1971 /> how the “elastic energy due to local twisting of the rod may be reduced if the central curve of the rod forms coils that increase its writhing number”.