Figure 33.23 The Mobius strip. The study of DNA structures has been enriched by a branch of mathematics called topology, which deals with structural properties unchanged by deformations such as stretching and bending. The Mobius strip, which has only one side, is an example of a topological structure. The Dutch graphic artist M. C. Escher illustrated the unique property of the Mobius strip by depicting ants crawling along the strip, always returning to the starting point after having traversed every part of the strip on both sides without ever crossing an edge.