The maximality of circular codes in genes has 20 preferential trinucleotides in each frame. This combinatorial property is statistically verified in the genes of both bacteria and eukaryotes, and by two approaches computing the trinucleotide occurrence frequencies in the 3 frames at the gene population level (classical method) and at the gene level (recent method). Several remarks explain why the codon usage parameter is unable to identify the circular codes. Some historical and theoretical considerations on comma-free and circular codes are presented. An evolutionary process by trinucleotide permutation is proposed to describe the transformation of a circular code (and its motifs) into another circular code.

基因中循环代码的最大值在每个框架中有 20 个优先三核苷酸。这种组合特性在细菌和真核生物的基因中都得到了统计验证，并通过两种方法在基因群体水平（经典方法）和基因水平（最近方法）计算 3 帧中的三核苷酸出现频率。几个注释解释了密码子使用参数无法识别循环代码的原因。介绍了关于无逗号和循环代码的一些历史和理论考虑。提出了通过三核苷酸排列的进化过程来描述一个循环密码（及其基序）到另一个循环密码的转换。