最近发现生物界密码子的一致性并不是过去所想象的那么绝对。密码子的三联性是一个较普遍的规律,从细菌到人类细胞所用的密码子都是三个硷基联在一起发挥效能的。从目前已有的资料,尚未见到有二联型或四联型的密码子。尽管这样,并不是说一个三联体肯定只和一种氨基酸发生联系(只编码一种氨基酸)。当然UGG只能编码色氨酸,也就是说色氨酸的密码子只是UGG。可是其它密码子就没有那么严格了,这就是密码子的兼并性。有的是二个密码子可编码同一种氨基 The recent discovery that the codons in the organism are consistent is not as absolute as it had been thought in the past. The triad of codons is a common rule that all three codons used from bacteria to human cells work together. From the information available to date, no codons have been found for di- or tetrad type. In spite of this, it does not mean that a triplet is definitely linked to only one amino acid (encodes only one amino acid). Of course UGG can only encode tryptophan, which means that the tryptophan codon is only UGG. However, other codons are less stringent, and this is codon usage. Some two codons can encode the same amino group