构建重组系统分析回文结构对基因表达的影响

回文结构序列是最常见的一种DNA序列，它是许多基因表达调控因子的顺式作用元件。本文设计了不同长度的回文结构序列，构建了Cre\|loxP重组系统，通过共转化含有cre基因的质粒和含有loxp位点的质粒，观察共转化菌株质粒图谱的变化，研究了重组系统在细菌中对基因表达的作用，同时研究不同长度回文结构对基因表达的影响，结果发现长度在20bp以下回文序列对下游基因的表达没有影响，而长于34bp的回文结构序列则会抑制下游基因的表达。

Analysis the Influence of Palindrome Structure to Gene Expression by Constructing Combination System

Palindrome sequence is very common in DNA,it usually acts as cis-elements of many regulative factors.In this paper,we design two palindrome sequences which is different in length,construct Cre-loxp combination system,then co-transform two kinds of plasmids,one contains cre gene,the other contains loxp site to E.coli DH5a strain.We judge the expression degree of cre gene in E.coli by examining the changes of plasmid maps of co-transformed strains,then conclude that 20bp or shorter than 20bp palindrome sequence uninhibit the expression of downstream genes,however,34bp or longer than 34bp palindrome sequence can inhibit that.