Now lets say you cut one strand of your DNA unthread it from

Now let\'s say you cut one strand of your DNA, \"unthread\" it from the other strand 2 times, reseal it into a circular molecule, and then again let it find its most stable state. What would the DNA look like now? [To understand what I mean by cut and \"unthread\", see the figure in our notes that shows a pair of scissors cutting one strand of DNA]

Solution

DNA that is cut and unwound can exist in right handed or left handed helical structure. Right handed helix contain twists are clockwise and moving away from the cut. The left handed helix contain twists that are anticlockwise coming close to point of cut. The above given DNA exists in left handed helix as shown at top of the figure. DNA in right handed helix exists as shown in bottom of the above figure. Mostly occuring form of DNA is B - DNA containing right handed helix. Therefore, the given DNA cut and unthread may exist as the figure shown at bottom of the given figure.