三种模式微生物基因组中GC含量的比较

GC含量是核酸序列组成的重要特征,其含量可作为反映进化的一种指标。为了探索GC含量作用于基因组的进化压力,本研究研究了大肠杆菌(Escherichia coli)和枯草杆菌(Bacillus subtilis)、真核生物酿酒酵母(Saccharomyces cerevisiae)三种模式微生物基因组编码序列的GC含量,分析了其基因组中蛋白质编码序列的GC含量与编码序列长度的关联,结果发现编码序列的GC含量与序列相对频数有一定的相关性,且编码序列的GC含量随序列相对频数的分布具有一定的规律。根据分布曲线我们推测这种规律应该符合某种分布,并用各种分布函数进行拟合,研究结果发现基因组中编码序列的GC含量随序列频数的分布与高斯分布相符合,且这种分布在真核生物和原核生物间有显著区别。另外,不同长度的编码序列GC含量的分析结果表明,编码序列的GC含量与序列长度有一定的相关性。

Comparison of GC Contents in Genomes of the Three Model Microbes

GC content is an important characteristic of nucleic acid sequence composition, which can be used as an index of evolution. In this research, in order to explore the evolutionary pressures of GC content in the genome, the GC contents of coding sequences in the genomes of three model microbes of Escherichia coli,Bacillus subtilis and Saccharomyces cerevisiae were studied, and the correlationship between GC content and length of the coding sequence were analyzed as well. The results indicated that there would be an existence of the correlationship between GC content of the coding sequence and the relative frequency of the sequence, and the GC content of coding sequence might have a certain rule with the relative frequency distribution of sequence.Therefore, we speculated that the law should conform to some kind of distribution based on the distribution curve, that would be a variety of distribution function to be fitted. The results found that the distribution of the GC content of the coding sequence with sequences relative frequency was consistent with the Gauss distribution,which was significantly different between eukaryote and prokaryote, and the results of GC content analysis of different length coding sequences show that the GC content of coding sequences has a certain correlation with the sequence length.