线粒体遗传密码及基因组遗传密码的对称分析

病毒、细菌和真核生物的氨基酸编码都使用相同的遗传密码，表明它们可能有共同的来源。但人和牛的线粒体的遗传密码和基因组的遗传密码相比，出现以下不同；（1）ATA编码甲硫氮酸M而不是异亮氨酸I。（2）TGA不再是终止密码子X而编码色氨酸W。（3）AGA和AGG不再是精氨酸R的密码子而变为终止密码子X。应用高维空间拓扑分析的方法，对线粒体遗传密码和基因组遗传密码的6维编码空间进行对称性分析，得到如下结果：（1）线粒体遗传密码的起始密码子是2个而不是1个。（2）线粒体遗传密码的终止密码子是4个而不是3个。（3）线粒体遗传密码空间只有2、4、6三种偶数简并度而没1、3两种奇数简并度，表明其对称度较高。（4）线粒体遗传密码空间除丝氨酸S分成两个平行的子空间之外，终止密码子X亦分成两个平行的子空间，表明其连通度较低。（5）线粒体遗传密码一基因组遗传密码相比，共有3个简并平面出现变异，即：1001λλ（M和I），011λ1λ（W和X），以及1011λλ（S和X或S和R）。（6）基因组遗传密码的1、3两种奇数简并度可能来源于线粒体遗传密码的1001λλ平面和011λ1λ平面的对称性破缺。对线粒体遗传密码变异的生物学意义及遗传密码的起源进行了分析和讨论。

SYMMETRICAL ANALYSIS OF THE MITOCHNODRIAL AND GENOMIC CODES

Virus, bacteria and eukaryocytes use the same genetic code table to encodes amino acids. It means that they would come from the same origin. But the mitochondrial genetic codes differ from the genomic genetic codes as follows: (1). ATA encodes methionine and not isoleucine; (2). TGA encodes tryptophane and not the terminate code; (3). AGA and AGG encode terminate codes and not arginine. A symmetrical analysis is made to compare the mitochondrial genetic codes with the genomic genetic codes and the following results can be obtained: (1). There are two initiate codes in the mitochondrial genetic codes as compared to one initiate code in genomic genetic codes; (2). There are four terminate codes in mitochondrial genetic codes as compared to three terminate codes in genomic genetic codes; (3). In mitochondrial genetic codes, there exist only 2, 4, 6, degeneracies of even number and lack of the 1 and 3 degeneracies of odd number; (4). In mitochondrial genetic codes, codons of serine are separated into two parallel isolated subspaces as well as the terminate codes; (5). Three degenerate planes appear variations in mitochondrial genetic codes as compare to the genomic genetic codes: 1001λλ(M and I), 011λ1λ(W and X), 1011λλ(S and X or S and R); (6). The appearance of 1 and 3 degeneracies of odd number in genomic genetic codes may originate from the symmetry breaking of the two degenerate planes 1001λλ and 011λ1λ of mitochondrial genetic codes. A common degenerate rule of connectivity of the genetic codons can be derived: " except the codons of serine which are separated into two independent subspaces, all the codons of the other 19 kinds of amino acids are degenerate through the λ degeneracy to form the unique and independent subspaces of connectivity. Three terminate codons in genomic genetic codes form a unique and connective subspace, while the four terminate codons in mitochondrial genetic codes are separated into two independent subspaces." The biological significance of the mitochondrial genetic codes and the possible evolution path of genetic codons are also analyzed and discussed.