Diagrammatic representation of the distribution of DNA bases and its applications

The frequencies of occurrence of the bases A, C, G and T (or U) in a DNA or mRNA sequence are denoted by a, c, g, t (or u), respectively. Since a + c + g + t = 1, the four real numbers are mapped into a point within a regular tetrahedron. The mapping points are then projected to some planes for further study. We have given several examples of application of this technique. As a by-product of an application we have found an empirical formula on the limit distribution of DNA bases for different kind of organisms, i.e. 1/4 less than or equal to a2 + c2 + g2 + t2 less than 1/3.