无义密码对线粒体密码进化的影响

遗传密码的起源与进化是理论生物学研究的一个基本问题.以线粒体密码为例,讨论密码进化关系构建的不同规则,分析密码进化中重要影响因素——无义密码子的再定义及其逆过程.终止信号与氨基酸间的距离是密码进化关系构建中的关键,在密码进化中无义密码子突变可以频繁进行,存在干涉现象,且进化倾向于无义密码子减少的方向.     

“扯淡”探源

始见于明代的"扯淡"一词文献习见,其中"淡"当为"诞"。"胡说"义是"扯淡"的引申义,该义来自"扯"的"闲谈"义和"诞"的"虚妄不实的言论"义。"拉"与"扯"语义相近,且有着相似的引申路径,所不同的是,"扯"已引申出"胡说"、"瞎说"义,而"拉"却没有。     

云南壮剧音乐中衬词的类型——云南壮剧音乐初探（之二）

衬词是戏曲音乐的重要组成部分。作为以本土腔为主要特征,融合其它声腔的多声腔少数民族剧种,云南壮剧音乐中的衬词更是丰富多彩,魅力无穷。经过对云南壮剧音乐中的衬词进行梳理和类比,可将他们分为起腔性衬词、特殊性衬词、称谓性衬词、填充性衬词、呼应性衬词、感叹性衬词、渲染性衬词和收腔性衬词等八种类型。     

中国艺术否定观刍议

“中国艺术否定观”的提出主要是基于中国文化传统和当前和谐社会文化构建的需要，其目的是既要接续中国文化传统，也要体现出当代中国文化现实的要求，其关键是如何处理现实矛盾，如何把握艺术对传统思想观念的“颠覆”问题。周星驰电影的无厘头无疑是这种否定观的范例。     

Yeast as a sensor of factors affecting the accuracy of protein synthesis

The cell monitors and maintains the fidelity of translation during the three stages of protein synthesis: initiation, elongation and termination. Errors can arise by multiple mechanisms, such as altered start site selection, reading frame shifts, misincorporation or nonsense codon suppression. All of these events produce incorrect protein products. Translational accuracy is affected by both cis- and trans-acting elements that insure the proper peptide is synthesized by the protein synthetic machinery. Many cellular components are involved in the accuracy of translation, including RNAs (transfer RNAs, messenger RNAs and ribosomal RNAs) and proteins (ribosomal proteins and translation factors). The yeast Saccharomyces cerevisiae has proven an ideal system to study translational fidelity by integrating genetic approaches with biochemical analysis. This review focuses on the ways studies in yeast have contributed to our understanding of the roles translation factors and the ribosome play in assuring the accuracy of protein synthesis.Received 27 November 2002; received after revision 16 April 2003; accepted 25 April 2003