Zhang C T, Zhang R
Department of Physics, Tianjin University, China.
Int J Biol Macromol. 1991 Feb;13(1):45-9. doi: 10.1016/0141-8130(91)90009-j.
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.
DNA或mRNA序列中碱基A、C、G和T（或U）的出现频率分别用a、c、g、t（或u）表示。由于a + c + g + t = 1，这四个实数被映射到一个正四面体内的一个点上。然后将这些映射点投影到某些平面上进行进一步研究。我们给出了该技术的几个应用实例。作为一个应用的副产品，我们发现了不同种类生物体DNA碱基极限分布的一个经验公式，即1/4 ≤ a² + c² + g² + t² ＜ 1/3。
