Nonetheless, DNA hairpin stem structure that generally embraces B-form with canonical base pairs is poorly understood in the context of periodic noncanonical A. .

Transition from B-to-Z is due to the mechanistic effect that originates from its pronounced nonisostericity with flanking canonical base pairs facilitated by base extrusion, backbone and/or base flipping.

Such DNA sequences tend to form unusual DNA structures comprising of base pairing schemes different from the canonical A. .

.C base pairs .

Influence of such unusual base pairing on the overall 3-dimensional structure of DNA and its impact on the pathogenesis of disorder is not well understood.

.A23 pair amidst canonical base pairs (Fig.

helix by measurements of the twist angle between consecutive base pairs , implementing the TwistFlex software previously developed [11] for the analysis of human fragile sites [3, 12] and its adaptation to fast long sequences analysis.

The conformation of DNA and its sequence dependence are mainly determined by the chemical structures of the base pairs and their interactions.

The computational model by Sarai et al [68] examines DNA flexibility on the basis of base pairs interactions and the results agree With available experimental observations.