[The extent of asymmetric distribution of DNA-bases in genes].

The correlation between the evolutionary rates of proteins and frequencies of DNA-bases in the first and in the second position of corresponding codons was investigated.Adenine in the first and guanine in the second position showed the strongest positive correlation with evolutionary rate whereas cytosine in the first as well as in the second position showed a strong negative correlation. The correlation can not be explained by a significant change in GC-content but rather by the asymmetric distribution of the base pairs. The extent of pyrimidine/purine asymmetry was assessed quantitatively.Variations in frequencies of bases lead to changed frequencies of neighbouring bases and thus to changed interactions between adjacent bases in the genes. Slowly evolving proteins are coded by genes with a maximum of thermodynamic interactions between the adjacent bases in the codogeneous chain as well as in the complementary chain. The genes for highly evolving proteins are characterized by minima interactions between adjacent bases.The possible relations between asymmetry and mutability of genes are discussed.