利用复杂网络来研究tRNA序列的进化

根据点突变和互补复制的进化机制构建tRNA序列相似度平行网络和反平行网络并研究了网络的特征．分析发现当相似度很大时，tRNA基因网络出现了无标度（scale—free）的特征．其次，还比较了平行网络和反平行网络的特征，发现在相同的条件下，反平行网络中的tRNA序列间的关系比平行网络中更密切，它们之间的相似程度更高．这同时说明现代tRNA序列由互补复制机制进化的可能性更大．最后根据点突变和互补复制的进化机制建立了一个粗糙的tRNA进化模型．结果发现模型tRNA相似度网络在0．3≤ε≤0．5条件下，不仅和真实tRNA相似度网络有局部的相似行为，而且网络的整体行为也是相似的．因此现代tRNA序列的合理的进化机制应该是上述两种机制的混合．

Using complex network to study the evolution of tRNA sequences

We constructed tRNA sequences parallel network and antiparallel networds and investigated the feature of the networks; we found that the networks behave scale-free properties when the similar degree is large. On the other hand,we compared the degree distribution of the tRNA sequences of the whole tRNA group in two type networks, and found that the tRNA sequences are more consanguineous in antiparalle than in parallel network, which seemed consistent with the ideal perfectly that modern tRNA sequences evolved by the complementary duplication. Finally, we presented a rough evolution model for modern tRNAs based on point mutation theory and the complementary method. The analysis indicated that the network of the tRNAs of the model has a similar network behavior with the real tRNAs network while . So, the evolution mechanism of the tRNAs should be the mixture of the point mutation and complementary duplication.