《生命科学》 2009, 21(1): 35-37

拷问双螺旋

徐有成*

美国德克萨斯大学达拉斯西南医学中心，美国

摘　要：摘　要：DNA真的完全是右旋的双螺旋吗(plectonemic)? 作者提出了一些疑问，并用实验证明质粒分子的拓扑环挠数可以为零，这是经典双螺旋结构不能解释的现象。据此实验观察以及若干其他证据，作者提出了关于DNA双螺旋结构的假说——左右旋共存的双螺旋(ambidextrous)，供研究和讨论。希望读者能革除先入之见，用开放的态度来独立思考、分辨是非、认真审视本文中不见于教材的新观点，从而作出自己明智的判断。
关键词：pBR322；旋转酶；左旋DNA；DNA复制；拓扑环绕数；8字结构

To interrogate the double helix

XU You-cheng*

University of Texas Southwestern Medical Center at Dallas， USA

Abstract: Abstract: Is DNA really right-handed (plectonemic) double helix? The author asked several questions and proved that the linking number of a plasmid could be zero， which is a phenomenon unexplainable by the traditional double helix model. Based on this observation and several other evidences， a hypothesis about the double helix was proposed. It is called ambidextrous double helix， in which the two strands are supposed to wind in both directions. This essay is provided for discussion. It is hoped that the readers can block their first impression， keep their minds open， to think carefully， independently， critically on the novel ideas that were not written in textbooks and to make their own judgments.
Key words: pBR322; gyrase; left-handed DNA; DNA replication; linking number; figure 8 structure