人类和黑猩猩的回文序列的对称性分析

Symmetry Analysis of an X-palindrome in Human and Chimpanzee

首次通过分析人类和黑猩猩的X染色体上的一条回文序列，来寻找这种对称性破缺的规律．分析结果表明，与红毛猩猩相比，尽管在人类回文序列上发生的突变总数比在黑猩猩上的少，但是在各自的序列上，它们的左臂的突变总数与右臂的突变总数都基本上是相同的，这意味着它们的回文序列的进化都是同步的．然而，在每个臂上，A／T→G／C的突变数目却大于G／C→A／T的，这表明回文序列的成分并没有达到平衡，并且GC含量有上升的趋势．此外，通过两臂之间的序列比较发现，发生在人类回文序列上的突变数目多于发生在黑猩猩上的突变数目，并且这种突变更容易发生在具有相似化学结构的碱基之间．因此，黑猩狠回文序列上的对称性看起来要比人类回文序列上的对称性高．

We analyze for the first time the rules of breaking in an X-palindrome between human and chimpanzee. Results indicate that although the overall changes that occurred in the human X-palindrome are fewer than in the chimpanzee, mutations occurring between the left arm and right arm were nearly equivalent both in human and chimpanzee when compared with orangutan, which implies evolutionary synchronization. However, there are many more A/T→G/C changes than G/C→A/T in a single arm, which would lead to an increasing trend in GC content and suggest that the composition is not at equilibrium. In addition, it is remarkable to find that there are much more asymmetrical nucleotide changes between the two arms of the human palindrome than that of the chimpanzee palindrome, and these mutations are prone to occur between bases with similar chemical structures. The symmetry seems higher in the chimpanzee palindrome than in the human X-palindrome.