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数理思维对生物学的奠基性贡献

时间:2016-07-09 14:11:00作者: 岳东晓的博文来源: http://blog.sciencenet.cn/blog-684007-989595.html


看了一篇文章,提到薛定谔1944年写的《生命是什么?》一书引发了生物学的革命。其实,数理科学对现代生物的决定性贡献远远早于薛定谔,而至少可以追溯到孟德尔(Mandel)。


孟德尔本来是一个物理学家,研究气象、气压之类。他用豌豆进行实验,有的豌豆粒是圆的,有的是皱的。他用纯种的圆豌豆跟纯种的皱豌豆杂交后,发现下一代豌豆全部是园的。然后,他用这杂交出来的圆豌豆培育下一代,发现四分之一的豌豆是皱的,四分之三是圆的。其实类似的实验达尔文也做过,也曾得到1:3的比例。但达尔文毕竟只是个观察敏锐的自然学家,对这种整数比例不敏感,也没去想这背后的机理。但孟德尔以其数理的底子,立刻意识到整数比例背后必有简单的机制。他从这个比例推出这是显性与隐性的遗传因子的作用的结果。孟德尔这个发现使人们对遗传机制有了更为清晰的理解,虽然并不知道遗传物质是什么。

放射性发现之后,有物理学家用射线轰击实验生物的样本,观察引起遗传突变的最小辐射剂量,从这个推断出遗传因子的大概由1000个原子组成。

薛定谔著名的是他的量子波动力学方程。在《生命是什么?》一书中,他对生物学从物理的角度进行了分析。当时生物学界认为蛋白质是遗传的载体。薛定谔根据物理原理做出下列判断:生物个体的发育及功能都是由染色体中的代码 (CODE)决定,细胞分裂时,代码被复制,在突变体中代码不再相同,而是在一处出现差异,用原子来编写这个代码就像摩尔斯电码(二进制),染色体内的代码纤维可以称为非周期性的有机晶体,这是生命的物质载体(“It is these chromosomes, or probably only an axial skeleton fibre of what we actually see under the microscope as the chromosome, that contain in some kind of code-script the entire pattern of the individual's future development and of its functioning in the mature state. ” “How do the chromosomes behave on mitosis? They duplicate -both sets, both copies of the code, duplicate.“ In the mutant the two copies of the code-script are no longer identical; they present two different 'readings' or 'versions', at any rate in that one place.” A well ordered association of atoms, endowed with sufficient resistivity to keep its order permanently, appears to be the only conceivable material structure that offers a variety of possible ('isomeric') arrangements, sufficiently large to embody a complicated system of ‘determinations' within a small spatial boundary.” “Indeed, the number of atoms in such a structure need not be very large to produce an almost unlimited number of possible arrangements. For illustration, think of the Morse code. The two different signs of dot and dash in well-ordered groups of not more than four allow thirty different specifications. ” “To give the statement life and colour, let me anticipate what will be explained in much more detail later, namely, that the most essential part of a living cell-the chromosome fibre may suitably be called an aperiodic crystal.” “Organic chemistry, indeed, in investigating more and more complicated molecules, has come very much nearer to that 'aperiodic crystal' which, in my opinion, is the material carrier of life. ” “We might quite properly call that an aperiodic crystal or solid and express our hypothesis by saying: We believe a gene -or perhaps the whole chromosome fibre -to be an aperiodic solid.”)。


薛定谔这个描述虽然纯粹是从物理角度进行推测,但已经给出了非常明确的探索方向。 这使不少本来研究物理的转向生物,包括Francis Crick 与 Maurice Wilkins。比这二人年青10来岁的 James Watson 在读了薛定谔的书后则是直接选择了生物专业。这三人在1953年发现了 DNA 的双螺旋结构。薛定谔的非周期性有机晶体终于被发现。

剩下的就是历史。