【作者】 李秋平；

【导师】 邱文元；

【作者基本信息】 兰州大学 ， 物理化学， 2008， 硕士

【摘要】 Chargaff第一和第二匹配规则构成了DNA双螺旋配对模型和单链上碱基数量关系的理论基石。在我们的研究中,我们对整个人类基因组进行了统计分析,引入了对称性的方法考察不同长度的碱基多联体(从2联体到6联体)和单个的碱基在各条染色体上的分布规律,对各种对称性在人类基因组中的表现形式进行了研究。在对人类基因组进行统计对称性考察的同时,还将各染色体的碱基组成与一条在单个碱基水平上按照Chargaff第二匹配规则生成的随机序列进行了对比分析。我们发现人类基因组在整体上遵守Chargaff第二匹配规则,具有镜像互补对称性。但是在局部范围内,人类基因组表现出了一定程度的对Chargaff第二匹配规则的背离,我们观察到在人类基因组中随着DNA序列长度的不断增大,它对Chargaff第二匹配规则背离就越小。同时,人类染色体与随机序列相比所表现出来的碱基分布不一致性,以及所具有的对称性不一致性,说明了在人类基因组中所表现出来的Chargaff第二匹配规则并不是由于人类染色体上所含碱基数量巨大而出现的统计现象,它的出现是基因组长期进化的结果。更多还原

【Abstract】 The first thing to study human genome is to figure out the statistical properties of base composition. In this paper we have studied human genome for the frequencies of occurrence of mononucleotides and oligonucleotides (from dinucleotides to hexnucleotides), and made a research to the form of the performance of the various symmetries in the human genome. Furthermore, then we have compared the statistical features of human genome to an artificial random sequence generated according to Chargaff’s second parity rule in mononucleotide level. We found that the human genome would comply with the Chargaff’s second parity rule, put another way, it possessed the mirror complementary symmetry. And local deviation has been observed in human chromosomes, and as the length of DNA segment, we observed increases the deviation to Chargaff’s second parity rule would decrease to a small extent. Human genome follows Chargaff’s second parity rule in large scale, nevertheless, the occurrence of oligonucleotides frequencies in human chromosomes differ with random sequences, and the symmetry inconsistency between them had shown that the obedience to Chargaff’s second parity rule for human genome shouldn’t be a subsequence of mathematics since the human chromosome sequences are of too long.更多还原