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題名 | 以DNA 序列估算演化差距 (1):九種植物物種間之演化差距 |
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作者姓名(中文) | 侯藹玲; 劉清; | 書刊名 | 中華農學會報 |
卷期 | 153 1991.03[民80.03] |
頁次 | 頁34-50 |
分類號 | 430.1635 |
關鍵詞 | DNA序列; 估算; 物種; 差距; 植物; 演化; |
語文 | 中文(Chinese) |
中文摘要 | 分子演化為以同源胺基酸或核苷酸序列等分子資料之差異,推測物種間之演化關係。比較二物種間之同源DNA序列時,可推算此二物種由共同祖先分歧至今的演化過程中,每個核苷酸位置上所發生之置換數,是為演化差距(evolutionary distance)的測度(K)。 演化差距的統計估算方法包括:Jukes與Canter⁽⁸⁾、Kimura⁽[92b7]⁾、Kimura⁽[8e67]⁾的3ST模式和2FC、Takahata與Kimura⁽[8fb2]⁾、Kaplan與Risko⁽⁹⁾、Gojobori等⁽⁷⁾以及Barry與Hartigan⁽²⁾的非同步模式和常速率模式。本文利用九種植物(藍綠藻、念珠藻、綠藻、菠菜、菸草、豌豆、玉米、大麥及水稻)之rbcL基因估算這些種間的演化差距以比較上述九種估算方法在應用上之異同。 九個物種間rbcL基因核苷酸序列三個字碼子位置上的演化差距分別以九種統計方法估算,其中以以物種間rbcL基因序列第三字碼子位置上之演化差距所估算之演化年代(x 10⁹年),每年每位置之平均置換速率為1.7x10⁻⁹次 Jukes與Cantor⁽⁸⁾所提之模式及Barry與Hartigan⁽²⁾的非同步模式出現不適用情況的機率最小,且發現第三位置上的演化差距較另二位置的大,且其估值之大小趨勢符合物種間親緣之遠近。又由已有證據之數種物種分歧年代,估算rbcL基因第三字碼子位置上之核苷酸置換速率,發現速率大致相等(約為每年每位置1.7×10⁻⁹個核苷酸),本文即以此平均速率來估算物種間的分歧年代。 本文中各種統計方法在演化差距小時,估算結果相近,但在估算遠緣物種之演化差距時,Jukes與Cantor⁽⁸⁾模式之估值最低,而Kimura⁽[8e67]⁾的2FC模式及Barry與Hartigan⁽²⁾的常速率模式則有較高之估值。 |
英文摘要 | Molecular evolution studies the phylogenetic relationship between species with the differences of molecular data, including homologous amino acid sequences and nucleotide sequences. By comparing homologous DNA sequences of two species, one can estimate the number of subsititutions per nucleotide site that have occurred during their descent from the common ancestor, which is defined to be the measure of evolutionary distances, K. Method of statistical estimation of evolutionary distance including Jukes & Cantor⁽⁸⁾, Kimura⁽¹¹⁾, 3ST and 2FC models of Kimura⁽¹²⁾, Takahata & Kimura⁽¹⁹⁾, Kaplan & Risko⁽⁹⁾ Gojobori et al, ⁽⁷⁾as well as asynchronous model and constant-rate model of Barry & Hartigan⁽²⁾. The DNA sequences data of rbcL gene from nine plant species (Anacystis, Anabaena, chlorella, spinach, tobacco, pea, maize, barley and rice) are used to estimate the evolutionary distance with nine stochastic methods stated above. The aim of this study is to compare the applicability as well as the relative magnitutes of the estimates of these methods. Evolutionary distances of DNA sequences of rbcL gene between any two of the nine sepecies are estimated by nine statistical methods at each of the three codon positions. The results show that the model of Jukes & Cantor⁽⁸⁾ and the asynchronous model of Barry & Hartigan⁽²⁾ have the lowest number of inapplicable cases. Also the estimated evolutionary distances at the third codon position of nine plant species are larger than those at the first and second codon positions, and agree with the relationships inferred from the conventional taxonomic categories. From the evidenced divergence times of several species, the rates of nucleotide subsititutions at the third codon position for rbcL gene, calculated form avolutionary distances, are almost equal (about 1.7×10⁻⁹ per site per year). The divergence times between any other two of the nine species are estimated with this rate. Statistical methods discussed in this paper all give similar estimates when the evolutionary distances is small. However, when estimating evolutionary distance of species far from each other, model of Jukes & Cantor gives the lowest figures whereas the 2FC model of Kimura and the constant-rate model of Barry & Hartigan tend to have higher distances. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。