arXiv:cond-mat/9803005v2 [cond-mat.soft] 18 Mar 1998 zhou.tex Bending and Twisting Elasticity: a Revised Marko-Siggia Model on DNA Chirality Zhou Haijun 1 and Ou-Yang Zhong-can 1,2 1 Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. Box 2735, Beijing 100080, China 2 Center for Advanced Study, Tsinghua University, Beijing 100084, China (October 13, 2018) Abstract A revised Marko-Siggia elastic model for DNA double helix [Macromolecules 27, 981 (1994)] is proposed, which includes the WLC bending energy and a new chiral twisting energy term. It is predicted that the mean helical re- peat length (HRL) for short DNA rings increases with the decreasing of chain length; while for very long chains, their mean HRL is the same, indepen- dent of both the chain length and whether the ends are closed, it is longer than the value for rectilinear DNAs. Our results are in good agreement with experiments. 87.10+e, 61.41+e, 87.15By Typeset using REVT E X 1