On the relative content of G,C bases in codons of amino acids corresponding to class I and II aminoacyl-tRNA synthetases.

We have analyzed the relative G,C content from protein coding regions of 530 organisms and found that the ratio of the G,C content of the codons of the amino acids corresponding to Class II and Class I aminoacyl-tRNA synthetases decreases in a statistically significant way from prokaryotes to animals. This can be interpreted assuming that an initial asymmetry between the G,C content of codons of Class I and II amino acids existed and has decreased in the course of evolution.