Why does the constitutive mutations OcO(operator)sequenceoccur frequently at left site of axis?Protected by repressoragainst methylationTGTTGTGTTTGTGTGTGACAACMethylationbeenhanced by repressor+251020mRNA startpointSymmetrical seq.of21bp&G/CasaxisT can be cross-linked to repressor(binding site)
Symmetrical seq. of 21 bp & G/C as axis Methylation be enhanced by repressor Protected by repressor against methylation T can be cross－linked to repressor(binding site) O (operator) sequence mRNA start point Why does the constitutive mutations OC occur frequently at left site of axis ?
O&Poverlap→repressor&RNApolymerasebindat sites that overlap around the start point of Lac operonrepressor &RNApol competition to overlapping site
O & P overlap repressor & RNA polymerase bind at sites that overlap around the start point of Lac operon repressor & RNA pol competition to overlapping site
操纵基因operator诱导物Three key factorsinducerof negative control调节基因in operonregulator
诱导物 inducer 调节基因 regulator 操纵基因 operator Three key factors of negative control in operon
RNA聚合酶催化乳糖分解的-酶基因转录11!-11阻遏蛋白阻遏失活迎诱导物乳糖
催化乳糖分解的 酶基因转录 阻遏蛋白 诱导物乳糖 RNA聚合酶
w.t. (I + O + P +) inducible typeaddinducer →operon onno inducer →operon offO C mut. (I + O C P+) constitutive mutationOC失去与repressor特异结合的能力
w.t. (I + O + P + ) inducible type O C 失去与repressor特异结合的能力 O C mut. (I + O C P + ) constitutive mutation add inducer operon on no inducer operon off