As gene type and function is fixed, species difference can also affect codon usage bias.The closer the consanguinity between species in evolution, the similar their codon usage bias is.

• 在基因的类型和功能一定的情况下，物种的差异也会影响到密码子的使用偏性，在进化上亲缘关系较近的物种间，其相对密码子使用概率也较接近。