Arquès D G, Michel C J
Equipe de Biologie Théorique, Université de Franche-Comté, Besançon, France.
J Theor Biol. 1995 Aug 21;175(4):533-44. doi: 10.1006/jtbi.1995.0161.
The mutation process is a classical evolutionary genetic process mainly based on the (random) substitutions of one base (A = Adenine, C = Cytosine, G = Guanine, T = Thymine) for another. Two analytical solutions derived here allow us to analyse in genes the occurrence probabilities of motifs (e.g. dinucleotides) after substitutions (in the evolutionary sense: from the past to the present) and, unexpectedly, also before substitutions (after back substitutions, in the inverse evolutionary sense: from the present to the past). We generalize on the alphabet [A, C, G, T] of the analytical solutions and of the properties derived on the alphabet [R, Y] (R = purine = A or G, Y = pyrimidine = C or T). Application of the theory is based on the analytical solution giving the probabilities of the 16 dinucleotides AA, ..., TT in the protein (coding) genes of (nuclear) eukaryotes, viruses and prokaryotes and in (eukaryotic) introns after back substitutions (called primitive genes). After back substitutions, four of 16 dinucleotides--CG, TA, GT and AC--occur with low probabilities in each of these four primitive gene populations, except for CG in the primitive prokaryotic protein genes. In the primitive eukaryotic protein genes, the dinucleotide AT has also a significant low probability. We present the properties of the two analytical solutions, and the functions which may have these five dinucleotides in primitive genes are described in terms of biological signals.
突变过程是一个经典的进化遗传过程，主要基于一个碱基（A = 腺嘌呤，C = 胞嘧啶，G = 鸟嘌呤，T = 胸腺嘧啶）被另一个碱基随机替换。这里得出的两个解析解使我们能够分析基因中替换后（从进化意义上讲：从过去到现在）基序（例如二核苷酸）的出现概率，而且出乎意料的是，也能分析替换前（反向替换后，从进化的反方向：从现在到过去）基序的出现概率。我们将解析解的字母表[A, C, G, T]以及在字母表[R, Y]（R = 嘌呤 = A 或 G，Y = 嘧啶 = C 或 T）上得出的性质进行了推广。该理论的应用基于给出真核生物（核）、病毒和原核生物的蛋白质（编码）基因以及反向替换后（称为原始基因）的（真核）内含子中16种二核苷酸AA、...、TT出现概率的解析解。反向替换后，在这四类原始基因群体中，16种二核苷酸中的四种——CG、TA、GT和AC——出现的概率较低，但原核生物原始蛋白质基因中的CG除外。在原始真核生物蛋白质基因中，二核苷酸AT出现的概率也显著较低。我们展示了这两个解析解的性质，并从生物信号的角度描述了这五种二核苷酸在原始基因中可能具有的功能。
