“…Our previous model, based on traditional fl uid dynamics, [6][7][8][9] has qualitatively revealed the reason why living beings employ only fi ve nitrogenous bases, i.e., two purines of A and G and three pyrimidines of T, C, and U, and also why purines and pyrimidines have a size ratio of about 1.5. However, the model had some gratuitous assumptions, and was also analyzed to the fi rst order of accuracy, which led to qualitative results only.…”