基因进化过程中核苷酸替代模型的比较分析

Analysing and Discussing on the Model of Nucleotide Substitution in Evolution of Genes

DNA序列中核苷酸替代数的估计是测定基因间进化距离的数学统计方法,是研究基因进化的基础.由于DNA分子包含多种序列区域等原因,核苷酸序列的替代模式比较复杂.最基本的核苷酸序列替代模型是p-距离模型J、ukes-Cantor模型、Kimura两参数模型.在此基础上衍生出其它一系列模型,如Tajima-Nei模型、Tamura模型、Tamura-Nei模型等.这些数学模型在拟合DNA序列进化的真实度时各有特点.这些模型中都假定各个位点的核苷酸替代速率一致,但实际情况并非完全如此,而是核苷酸的替代速率近似地遵循Г分布.

Estimating of substitution number of nucleotide in DNA sequences is a basic statistic method of measuring evolution distance between genes, which is the base of researching molecular evolution of genes. Mode of nucleotide substitution in DNA sequences is very complex, due to various types of DNA sequence contained in DNA and other causes, p - distance model, Jukes - Cantor model and Kimura - two paramers model are basic models of nucleotide substitution in DNA sequences, from which the other models, such as Tajima- Nei model, Tamum model and Tamura- Nei model are derived . These models have their own advantages and defects in simulating evolution of DNA sequences and the authors analysed and discussed them, respectively. There is a tentative premise in these models： identical rates of nucleotide substitution exist at all positions of nucleotide substitution. However,the case is not true and substitution rates of nucleotides, approximately, follow asГ-distribution. In this paper, authors also discussed the case.