自组织课件.pptVIP

error catastrophe an error-free system has a selection advantage S over a system with an error. The survival criterion is then: N ·w logS If the above condition is to be fulfilled, the error rate cannot be larger than 1/N. they needed to survive with error rates of more than 1:100; this reduced the size of the genome to around 100 bases (nucleotides). experiments with the Q beta phage For his in vitro incubation experiment, Spiegelmann used: purified Q beta-RNA, Q beta-replicase and the four ribonucleoside triphosphates (ATP, GTP, UTP and CTP). After 20 min, he transferred part of the reaction mixture to a fresh reaction medium (with replicase and nucleotides): 75 such transfer reactions were carried out. The incubation time was successively reduced, in order to select the RNA species initially formed; the rate of RNA synthesis increased from reaction to reaction. The length of the virus RNA decreased considerably and was finally only 17% of the initial length. M. Eigen carried out similar experiments with the Q beta phage (Biebricher et al., 1981). He decreased the concentration of added viral RNA stepwise but still obtained a good yield of mutant RNA, the chain length of which was, however,decreased information crisis The “information crisis”, i.e., the fact that, because of the error frequency, longer RNA chains have so many errors after only a few reproduction steps that they can no longer be replicated, cries out for catalysts which can guarantee more exact replication.While only protein catalysts (enzymes) had been discussed until recently, ribozymes are now possible candidates. More complex catalysts would have required more complex matrices; but where did the matrix molecules come from? 反应循环 催化循环 超循环 4、系统科学简介 从简单到复杂 从确定到不确定 1+1 2? 一般系统论 Ludwig von Bertalanffy 美籍奥地利理论生物学家。一般系统论的创始人，从物理学、生物学与心理学探讨同型性的系统论原理，1952年发表抗体系统论，60年代提出应用开放系统论于生物学研究的概念、方法与数学模型等，奠基了系统生物学，并导致了系统生态学、系统生理学的学科体系发展，以及影响了中国生物学家曾邦哲20世纪90年代提出系统医学、系统遗传学与系统生物工程的概念与原理。1901年9月19日生于奥地利首