Supercoiling

Supercoiling is a property of a DNA double helix in which the number of turns of the two strands around each other either exceed or are fewer than the number of turns in the most stable helical conformation. Only a helix that is circular or else fixed at both ends can support supercoiling. The energy stored in circular DNAs by twisting them into supercoils may have major effects on DNA conformation.

See also: Figure 4.24, Twist, Writhe, Linking Number, Topoisomerases, Circular DNA and Supercoiling