Duplices

In addition to the A and B forms of DNA, there is a third form (C-DNA). It is essentially very similar to B-DNA but the duplices are packed differently in the fibre and moreover the number of base pairs per full turn of the helix is not an integer (Marvin, Spencer, Wilkins and Hamilton, 1961).

Hypochromicity studies have shown that these duplices are less stable than either the totally complementary duplex or those containing A.C. and G.T mismatches.

Nucleic acid duplices can be reversibly dissociated into single strands and several parameters may drive the de/renaturation one way or the other.

These polymer chains are not typically found as paired duplices, but rather as complex forms that comprise paired segments and loops that are often stabilized by metal ions.