[农学]原核基因表达调控.pptVIP

第九15原核基因表达调控;;本章重难点;第一节 乳糖系统和操纵子模型;Operator is the site on DNA at which a repressor protein binds to prevent transcription from initiating at the adjacent promoter.Repressor protein binds to operator on DNA or RNA to prevent transcription or translation, respectively.Structural gene codes for any RNA or protein product other than a regulator.;regulator gene codes for a protein that acts at a target site on DNA. ;In negative control, a trans-acting repressor binds to the cis-acting operator to turn off transcription. In prokaryotes, multiple genes are controlled coordinately. ;In positive control, trans-acting factors must bind to cis-acting sites in order for RNA polymerase to initiate transcription at the promoter. In a eukaryotic system, a structural gene is controlled individually.;Operon is a unit of bacterial gene expression and regulation, including structural genes and control elements in DNA recognized by regulator gene product(s).; 乳糖操纵子学说;一、酶的诱导;; 二、结构基因和调节基因的突变 ;The lac operon occupies ~6000 bp of DNA. At the left the lacI gene has its own promoter and terminator. The end of the lacI region is adjacent to the promoter, P. The operator, O, occupies the first 26 bp of the long lacZ gene, followed by the lacY and lacA genes and a terminator. ;为了和野生型相区别，两类突变型分别以下列符号标记：;三、调节基因;由上述实验及结果分析，可以建立下述模型：;四、Jacob-Monod的负控制模型及实验依据;;五、I基因产物及功能;; ic p o Z Y A;iS p o ;;六、操纵区和启动区;O gene (operator) cis-action factor;O gene (operator) cis-action factor;O gene (operator) cis-action factor;O gene (operator) cis-action factor;O gene (operator) cis-action factor;---调控机理;w.t. (I+ O+ P+) 诱导型;iC mut. (iC O+P+) constitutive mut. (组成型);八、P-O区的结构 ;第二节 半乳糖操纵子;;一、cAMP-CAP对两个gal启动子的不同作用 ;;二、双启动子的生理功能;三、双操纵区 ;第三节 色氨酸操纵子;trpR P O E D C B A;一、色氨酸操纵子的阻遏–操纵系统;二、弱化子和前导区 ;三、mRNA的前导区全序列分析 ; d) 调控机制分析;调控机制分析;;四、弱化的机制;五、色氨酸操纵子弱化机制的??验依据;第四节 入噬菌体基因表达的调节