沃森和克利描述结构的脱氧核糖核酸137030032.doc

Watson and Crick describe structure of DNA(1953)Photo: Model of DNA molecule In the late nineteenth century, a German biochemist found the nucleic acids, long-chain polymers of nucleotides, were made up of sugar, phosphoric acid, and several nitrogen-containing bases. Later it was found that the sugar in nucleic acid can be ribose or deoxyribose, giving two forms: RNA and DNA. In 1943, American Oswald Avery proved that DNA carries genetic information. He even suggested DNA might actually be the gene. Most people at the time thought the gene would be protein, not nucleic acid, but by the late 1940s, DNA was largely accepted as the genetic molecule. Scientists still needed to figure out this molecules structure to be sure, and to understand how it worked. In 1948, Linus Pauling discovered that many proteins take the shape of an alpha helix, spiraled like a spring coil. In 1950, biochemist Erwin Chargaff found that the arrangement of nitrogen bases in DNA varied widely, but the amount of certain bases always occurred in a one-to-one ratio. These discoveries were an important foundation for the later description of DNA. In the early 1950s, the race to discover DNA was on. At Cambridge University, graduate student Francis Crick and research fellow James Watson (b. 1928) had become interested, impressed especially by Paulings work. Meanwhile at Kings College in London, Maurice Wilkins (b. 1916) and Rosalind Franklin were also studying DNA. The Cambridge teams approach was to make physical models to narrow down the possibilities and eventually create an accurate picture of the molecule. The Kings team took an experimental approach, looking particularly at x-ray diffraction images of DNA. In 1951, Watson attended a lecture by Franklin on her work to date. She had found that DNA can exist in two forms, depending on the relative humidity in the surrounding air. This had helped her deduce that the phosphate part of the molecule was on the outside. Watson returned to Cambridge with a rather muddy recollection of the facts Franklin had presented, though clearly critical of her lecture style and personal appearance. Based on this information, Watson and Crick made a failed model. It caused the head of their unit to tell them to stop DNA research. But the subject just kept coming up. Franklin, working mostly alone, found that her x-ray diffractions showed that the wet form of DNA (in the higher humidity) had all the characteristics of a helix. She suspected that all DNA was helical but did not want to announce this finding until she had sufficient evidence on the other form as well. Wilkins was frustrated. In January, 1953, he showed Franklins results to Watson, apparently without her knowledge or consent. Crick later admitted, Im afraid we always used to adopt - lets say, a patronizing attitude towards her. Watson and Crick took a crucial conceptual step, suggesting the molecule was made of two chains of nucleotides, each in a helix as Franklin had found, but one going up and the other going down. Crick had just learned of Chargaffs findings about base pairs in the summer of 1952. He added that to the model, so that matching base pairs interlocked in the middle of the double helix to keep the distance between the chains constant. Watson and Crick showed that each strand of the DNA molecule was a template for the other. During cell division the two strands separate and on each strand a new other half is built, just like the one before. This way DNA can reproduce itself without changing its structure - except for occasional errors, or mutations. The structure so perfectly fit the experimental data that it was almost immediately accepted. DNAs discovery has been called the most important biological work of the last 100 years, and the field it opened may be the scientific frontier for the next 100. By 1962, when Watson, Crick, and Wilkins won the Nobel Prize for physiology/medicine, Franklin had died. The Nobel Prize only goes to living recipients, and can only be shared among three winners. Were she alive, would she have been included in the prize? 翻译：沃森和克利描述结构的脱氧核糖核酸1953图片：模型脱氧核糖核酸分子 在第十九世纪末，德国生物化学家发现核酸的核苷酸，长链聚合物，是由糖，磷酸，和一些含氮碱基。后来发现，糖，核糖或脱氧核糖核酸可，两家形式：核糖核酸和脱氧核糖核酸。1943，美国奥斯瓦尔德埃弗里证明脱氧核糖核酸携带遗传信息。他甚至建议实际上可能是基因的脱氧核糖核酸。那时许多人认为基因是蛋白质，没有核酸，但到40年代后期，脱氧核糖核酸，在很大程度上接受的遗传分子。科学家还需要找出这种分子的结构确定，并了解它是如何工作的。 1948年，莱纳斯鲍林发现许多蛋白质形状的螺旋，螺旋弹簧线圈。1950年，生物化学家欧文查发现，安排氮碱基差异很大，但数额依据总是发生在一对一的比例。这些发现是一个重要的基础，后来的描述脱氧核糖核酸。早在20世纪50年代，比赛被发现脱氧核糖核酸。在剑桥大学，研究生弗兰西斯沃森和杰姆斯研究员（1928）已成为感兴趣，尤其是鲍林的工作留下深刻的印象。同时在伦敦国王学院，毛里斯威尔金斯（公元1916），罗瑟琳也研究基因。剑桥队的做法是使物理模型缩小的可能性，并最终建立一个准确的图片的分子。国王队参加了一个实验的方法，特别是在X射线衍射图像的脱氧核糖核酸。1951年，出席讲座的在她工作的日期。她发现基因的存在形式，取决于相对湿度在周围的空气。这有助于她推断，磷酸盐分子的一部分，就在外面。沃森返回剑桥与一个相当泥泞回忆事实Frank lin提出了批评，尽管她的演讲风格和个人的外观。根据这一信息，沃森和克利失败了模型。它使单位领导人告诉他们停止研究。但问题就来了。法兰克林，主要工作，发现她的X射线衍射表明，“湿”形式的脱氧核糖核酸（在高湿度）的所有特征的一个螺旋。她怀疑所有NA螺旋但不想公布这个发现，直到她有足够的证据对其他形式以及。威尔金斯很沮丧。在一月，1953，他表现的结果，显然没有她的同意或知识。后来承认，“我担心我们常采用让我们说，光顾对她的态度。”沃森和肌肉痉挛了关键的概念性的一步，表明分子是由双链核苷酸，每在一个螺旋Frank lin已经找到，但要等下。刚学查结果的碱基对在1952的夏天。他补