Operons are either RNa polymerase cant bind inducible transcription blocked or repressible according Repressor bound the control to operator mechanism. Seventy pia Plac five different operons controlling 250 Inducer structural genes have Active repressor (lactose) been identified for e RNa polymerase binds Inducer bound coli. Both repression to repressor and induction are examples of negative contro since the Transcription mRNA transcript proceeds repressor proteins turn off transcription
Operons are either inducible or repressible according to the control mechanism. Seventyfive different operons controlling 250 structural genes have been identified for E. coli. Both repression and induction are examples of negative control since the repressor proteins turn off transcription
Low glucose Trp absent RNA polymerase CRPO O CAMP RNA polymerase Transcription mRNA binds to proceeds IP-CAME transcript complex promoter complex (enhancer) Transcription proceeds nactive 3 repressor High glucose Corepressor ( tryptophan RNA polymerase cant bind Trp present Active Structural genes repressor not transcribed RNA polymerase Active repressor bound td can't bind operator, transcription blocked 0 C5
有效转录的基本条件 酩1动子( promoter.):在基因序列中,标志着转录起始的可 IA聚合酶识别的位点DNA区段),一般位于基因的上游 终止子( terminator):位于基因的编码序列之外(一般在 下游)的一段标志着转录停止的RNA聚合酶识别位点。 Prokaryotic gene regulation differs from eukaryotic regulation, but since prokaryotes are much easier to work with, we focus on prokaryotes at this point. Promoters are sequences of dna that are the start signals for the transcription of mRNA. Terminators are the stop signals. mRNA molecules are long(500- 10,000 nucleotides)
启动子（promoter）：在基因序列中，标志着转录起始的可 被RNA聚合酶识别的位点(DNA区段)，一般位于基因的上游。 终止子（terminator）：位于基因的编码序列之外（一般在 下游）的一段标志着转录停止的RNA聚合酶识别位点。 有效转录的基本条件 Prokaryotic gene regulation differs from eukaryotic regulation, but since prokaryotes are much easier to work with, we focus on prokaryotes at this point. Promoters are sequences of DNA that are the start signals for the transcription of mRNA. Terminators are the stop signals. mRNA molecules are long (500- 10,000 nucleotides)
第一节基因表达的基本条件 1、基因表达的基本过程 2、有效转录的基本条件 3、正确翻译的基本条件 4、影响克隆基因表达效率的因素
第一节 基因表达的基本条件 1、基因表达的基本过程 2、有效转录的基本条件 3、正确翻译的基本条件 4、影响克隆基因表达效率的因素
正确翻译的基本条件 The genetic Code To code for the 20 essential amino acids a genetic code must consist of at least a 3-base set (triplet) of the 4 bases. If one considers the possibilities of arranging four things 3 at a time (4X4X4), we get 64 possible code words, or codons(a 3-base sequence on the mrna that codes for either a specific amino acid or a control word). The genetic code was broken by marshall Nirenberg and Heinrich Matthaei, a decade after watson and Crick's work, The genetic code consists of 61 amino-acid coding codons and three termination codons, which stop the process of translation. The genetic code is thus redundant(degenerate in the sense of having multiple states amounting to the same thing), with, for example, glycine coded for by GGU, GGC, GGA, and GGG codons
The Genetic Code To code for the 20 essential amino acids a genetic code must consist of at least a 3-base set (triplet) of the 4 bases. If one considers the possibilities of arranging four things 3 at a time (4X4X4), we get 64 possible code words, or codons (a 3-base sequence on the mRNA that codes for either a specific amino acid or a control word). The genetic code was broken by Marshall Nirenberg and Heinrich Matthaei, a decade after Watson and Crick's work. The genetic code consists of 61 amino-acid coding codons and three termination codons, which stop the process of translation. The genetic code is thus redundant (degenerate in the sense of having multiple states amounting to the same thing), with, for example, glycine coded for by GGU, GGC, GGA, and GGG codons. 正确翻译的基本条件