【摘要】 以ＧＣＧ软件和数学模型为工具，用观察到的某ＤＮＡ序列的频数（Ｏ）与理论计算出的此序列频数（Ｔ）的比值（Ｏ／Ｔ）为参数（即相对频数），将基因资料库（包括ＧｅｎＢａｎｋ和ＥＭＢＬＤａｔａＢａｓｅ）的ＤＮＡ序列进行了分析．结果显示ＤＮＡ重复序列的分布存在着如下趋势：（１）越简单的ＤＮＡ重复序列，其相对频数越高，离平衡分布越远；（２）顺向重复序列的分布的相对频数高于反向重复序列的分布；（３）较长的保守序列的相对频数较高；（４）含ＡＴ碱基对的重复序列的相对频数高于含ＧＣ碱基对的重复序列，在较长的ＤＮＡ重复序列中尤其明显：（５）上述ＤＮＡ重复序列分布的趋势存在种属特异性．更多还原

【Abstract】 The five trens of global DNA composition on simple repetitive tretches were revealed by scanning the DNA databases using the GCG program and by analysing the data using a mathematical model.The calculation of the ratio of observed frequency to the theoretical frequency (O/T) allowed different repetitive stretches to be compared with each other on a common ground.It is thus revealed that the global DNA composition is phylogenetically constrained such that the following trends are exist.(Ⅰ)Simplicity is prevailing.The simpler the stretches,the higher the O/T ,that is expressed as (X) a >(XY) a /2 >(XYZ) a /3 >(XWZT) a /4 .(X,Y,W,Z,stands for different base pairs and “ n ”and “ a ” refer to positive round number).(Ⅱ)Tandem stretches are higher in O/T than reverse stretches.It is expressed as (XYXY) n >(XYYX) n. (Ⅲ)Conserved stretches are constrained such that the longer the stretches,the higher the O/T to a certain extent.This is expressed as (XY) a >(XY) a -1 >(XY) a -2 >(XY) a -3 …….(Ⅳ)The stretches containing AT base pairs are higher in O/T than the stretches containing GC base pairs,especially in longer stretches.(Ⅴ)The global DNA composition is organismic specific.The organismic specificity is shown on the different exponential slops of the ln O/T in a macroscopic manner.更多还原