遗传密码的进化稳定性

本评述了遗传密码的进化有关的物理问题。主要讨论了：1）从进化稳定性的观点研究遗传密码的简并规则,证明了现有密码表中多重态的简并规则是突变危险性极小的;2）从进化稳定性的观点研究了遗传密码表中氨基酸和终止密码子的排布,导出了总体突变危险性极小的表,并证明了标准密码表是在某些约束（这些约束反映了密码形成时期的初始条件）下总体突变危险性极小的表;3）密码表中20种氨基酸和终止密码简并度的分布,以及改变简并度条件下密码反常的出现。

THE EVOLUTIONARY STABILITY OF GENETIC CODE

The construction of genetic code is investigated based on stability principle.The concept and formulation of mutational deterioration (MD) of genetic code are proposed.It is proved that the degeneracies of code multiplets obey the rule to resist best to the mutational deterioration. The MD for each ideal multiplet of codons is expressed by 4 parameters and the arrangement of the real multiplet takes MD minimum.Then the global mutational deterioration (GMD) of code table is calculated and the minimal code is deduced.The domain?like distribution of hydrophobic and hydrophilic amino acids on genetic code is explained from the minimization of GMD.It is demonstrated that the standard code is approximately GMD?minimal (at a level of 90%) and the code is deducible.By introducing some constraints we have deduced the standard genetic code from the minimization of GMD.The minimization shows the evolutionary stability and the constraint is a statement on "frozen accident".The change of multiplicity of amino acids and terminators is discussed.The deviant codon assignments are studied in the framework of MD theory and have been explained partly through the stability?favorable re?arrangement process of codons.