Barbieri Marcello
Dipartimento di Morfologia ed Embriologia, Via Fossato di Mortara 64a, 44121 Ferrara, Italy.
Biosystems. 2019 Jul;181:11-19. doi: 10.1016/j.biosystems.2019.04.010. Epub 2019 Apr 17.
For a long time it has been assumed that the rules of the genetic code were determined by chemistry - either by stereochemical affinities or by metabolic reactions - but the experimental evidence has revealed a totally different reality; it has been shown that any codon can be associated to any amino acid, and this means that there is no deterministic link between them. The genetic code, in other words, is based on arbitrary, or conventional, rules and this raises a formidable problem: how can arbitrary rules exist in Nature? We know that such rules exist in culture, but there is an abyssal difference between biology and culture, because the cultural codes are short-lived, whereas the biological codes are the most conserved entities in evolution. Biological codes, in other words are fundamentally different from cultural codes and we do need a model that makes us understand how they came into being. In this paper it is shown that the origin of biological codes takes place in five phases (beginning, evolution, optimization, major transition and conservation) and this suggests a general model for their development. According to this model, a biological code evolves in a system as a means of solving a local problem, but then it becomes the tool of a much larger change in macroevolution. This is the great potential of the biological codes: their ability to bring into existence absolute novelties that change the whole course of the history of life. Different major transitions were based on different codes, but we can also recognize some common features in all of them. This indicates that coding is a universal mechanism that Nature has employed many times in the course of evolution to solve a wide variety of different problems.
长期以来，人们一直认为遗传密码的规则是由化学决定的——要么是通过立体化学亲和力，要么是通过代谢反应——但实验证据揭示了一个完全不同的现实；已经表明，任何密码子都可以与任何氨基酸相关联，这意味着它们之间不存在确定性联系。换句话说，遗传密码是基于任意的或约定俗成的规则，这就引发了一个巨大的问题：自然界中怎么会存在任意规则呢？我们知道这种规则存在于文化中，但生物学和文化之间存在着巨大的差异，因为文化密码是短暂的，而生物密码是进化中最保守的实体。换句话说，生物密码与文化密码有着根本的不同，我们确实需要一个模型来让我们理解它们是如何产生的。本文表明，生物密码的起源发生在五个阶段（开始、进化、优化、重大转变和保守），这为它们的发展提出了一个通用模型。根据这个模型，生物密码在一个系统中作为解决局部问题的一种手段而进化，但随后它成为宏观进化中一个更大变化的工具。这就是生物密码的巨大潜力：它们能够带来绝对的新奇事物，从而改变生命历史的整个进程。不同的重大转变基于不同的密码，但我们也能在所有这些转变中识别出一些共同特征。这表明编码是一种通用机制，自然界在进化过程中多次使用它来解决各种各样不同的问题。
