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人类基因组由一些较长的,G+C含量相对均匀的DNA片段组成,也就是我们所说的isochore结构。Isochore结构与许多重要的生物学特征相关,如:基因密度、CpG岛等,关于这些已有系统的研究。我们使用基于Z曲线理论的基因组序列分段算法,在单核苷酸精度的水平上定位了人类基因组56个isochore的边界,共得到79个独立的边界。我们发现在这79个边界中,45.6%的isochore边界在与17个脊椎动物基因组比对时,显示出明显的保守性,比如:某段高保守的序列在isochore边界处转换为一段弱保守或者完全不保守序列。另外isochore边界附近的序列组成高度保守。通过和已被实验证实的复制开关点附近的序列相比较。有理由推断这79个isochore边界都有可能是人类基因组中的复制开关位点,这一点有待实验验证。
The human genome consists of relatively long DNA fragments of relatively uniform G + C content, what we call the isochore structure. Isochore structure is associated with many important biological features such as gene density, CpG islands, etc., and studies on these existing systems. Using genomic sequence segmenting based on Z-curve theory, we mapped the borders of the 56 isochore of the human genome at the level of single-nucleotide accuracy and obtained 79 independent borders. We found that 45.6% of the isochore boundaries among the 79 boundaries show significant conservation when aligned with 17 vertebrate genomes, such as a highly conserved sequence that is converted to a weakly conserved region at the isochore boundary or No conservative sequence at all. In addition the sequence composition near the isochore boundary is highly conserved. Compare with sequences that have been experimentally confirmed near duplicate switch points. It is reasonable to conclude that all of these 79 isochore boundaries are likely to be replicative switch sites in the human genome.