[Constraints acting on the base sequence in a polynucleotide. II. Distribution of complementary tetranucleotides in genes of Escherichia coli and bacteriophages lambda and T7].

The complementary tetranucleotides tend to be equally favoured or avoid in E. coli, lambda and T7 genes. Constraints exist that act equally on nucleotide sequence of each one of both strings of DNA molecule, without any relation with the lecture phase.