The genetic code has evolved from its initial non-degenerate wobble version until reaching its present state of degeneracy. By using the stereochemical hypothesis, we revisit the problem of codon assignations to the synonymy classes of amino-acids. We obtain these classes with a simple classifier based on physico-chemical properties of nucleic bases, like hydrophobicity and molecular weight. Then we propose simple RNA (or more generally XNA, with X for D, P or R) ring structures that present, overlap included, one and only one codon by synonymy class as solutions of a combinatory variational problem. We compare these solutions to sequences of present RNAs considered as relics, with a high interspecific invariance, like invariant parts of tRNAs and micro-RNAs. We conclude by emphasizing some optimal properties of the genetic code.

中文翻译：

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进化和 RNA 遗迹。系统生物学观点

遗传密码已经从最初的非退化摆动版本进化到目前的退化状态。通过使用立体化学假设，我们重新审视了氨基酸同义类别的密码子分配问题。我们使用基于核酸碱基的物理化学特性（如疏水性和分子量）的简单分类器获得这些类别。然后，我们提出了简单的 RNA（或更普遍的 XNA，X 代表 D、P 或 R）环结构，这些结构呈现、重叠包括一个且仅一个同义词类的密码子，作为组合变分问题的解决方案。我们将这些解决方案与被视为遗物的现有 RNA 序列进行比较，这些 RNA 具有高度的种间不变性，如 tRNA 和微 RNA 的不变部分。我们最后强调遗传密码的一些最佳特性。