Phase transition between A and B forms of DNA: a free-energy perspective.

We study the structural transition from B form of DNA to A form of DNA using group theoretic methods. The transition is not of the order-disorder type and hence to construct a Landau kind of theory for the transition we define a higher symmetry and relevant order parameters. We also discuss the issue of all the conformations, observed experimentally during the course of transition, being fundamentally different or not.