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    請使用永久網址來引用或連結此文件: http://ir.lib.ncu.edu.tw/handle/987654321/7407


    題名: 演化複製的足跡 - 基因體的普適等價長度;The Footprint of Evolution Duplication - Universal Equivalent Length of Genomes
    作者: 陳鴻大;Hong Da
    貢獻者: 物理研究所
    關鍵詞: 演化;RNA世界;複製;等價長度;Evolution;Duplication;Equivalent Length;RNA word
    日期: 2009-07-15
    上傳時間: 2009-09-22 10:57:24 (UTC+8)
    出版者: 國立中央大學圖書館
    摘要: 複製事件廣泛存在基因體的歷史當中,主導了基因序列的成長與演化。為了比較不同基因體間複製演化的共同特性,我們定義了序列的等價長度 l_e,等度價長度的直接意義即是,這個序列與長度 l_e 的隨機序列具有"等價的隨機性質"。也就是說,隨機序列的等價長度即等於自身的序列長,等價長度會在序列遭受隨機突變時增長,而在序列被複製時保持不變。 根據我們的研究,基因體具有普世的等價長度,且在染色體不同部分的等價長度皆相同,顯示原始的基因序列可能開始於一短序列,經由隨機片段複製作為演化動力而成長。這個結論與 RNA 世界假說相符合,而且能夠解釋存在先今基因體當中頻密的複製事件,或許也可為演化速率不平均的爭議提供解答。 Segmental duplication is widely held to be a dominant feature in the dynamics of genome growth and evolution. Yet how this would a ect the global structure of genomes has not been discused. Here, we identify the equivalent length, Le, of a genomic sequence as a medium through which that dominance may be discussed quantitatively. Through examining 865 complete chromosomes we nd the Le for a genomic sequence to be nearly invariant and remarkably short compared true sequence length { in terms of the statistics of two-letter words it is about 300 bases long { and is approximately universal for all (examined) complete chromosomes. We verify this result to be non-trivial, in particular, not caused by the similarity of sequences in any commonly held sense, and demonstrate that it is easy to generate genome-like sequences not having universal Le's. We establish a causal relation between short Le and segmental duplication and show that a simple, random-segmental-duplication driven model for genome growth generates highly diverse genome-like sequences that have universal Le's. We postulate a connection between the universal value of Le and maximum information capacity in genomic sequences and infer that the universality of Le is a crucial product of the evolution of genome toward maximum tness.
    顯示於類別:[物理研究所] 博碩士論文

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