[Ring closed DNA. The theory of formation of the first supercoil]

The equilibrium configurations of the ring closed DNA molecule, from the ring closed form to the formation of the first supercoil (in the form of eight), have been determined by the methods of the elasticity theory. The description of the topological characteristics allows one to investigate the linking number, twisting, the writing number, and supercoiling degree immediately from the model for any equilibrium configuration of the DNA molecule. This enables one to estimate the influence of external factors on the properties and the state of ring closed DNA molecules.