泽克廷大学 上 Shanghai Jiao Tong University 1896 1920 1987 2006 Lecture 7-3 Principles of Microbial Molecular Biology Chapter 6 in BROCK BIOLOGY OF MICROORGANISMS JIAO TONG Chen Feng School of Life Science and Technology Shanghai Jiao Tong University http://micro.sjtu.edu.cn Email:cf2001@sjtu.edu.cn
1896 1920 1987 2006 Lecture 7-3 Principles of Microbial Molecular Biology Chen Feng School of Life Science and Technology Shanghai Jiao Tong University http://micro.sjtu.edu.cn Email: cf2001@sjtu.edu.cn Chapter 6 in BROCK BIOLOGY OF MICROORGANISMS
上泽充通大学 Shanghai Jiao Tong University Transcription:Discuss the following questions 1.Why do we need a messenger RNA? 2.RNA polymerase:Any direction?Why? 3.RNA polymerase:Need a primer? 4.Initiation of RNA synthesis:How to find the right place? Where is the right place?Which DNA strand is the right strand for transcription? 5.Termination of RNA synthesis:where is the right place for termination? 6.Transcription:write down the relative position of promoter position,terminator,start codon,stop codon for a polycistronic mRNA No. 2 Chen Feng.Shanghai Jiao Tong University
No. 2 Chen Feng, Shanghai Jiao Tong University Transcription: Discuss the following questions 1. Why do we need a messenger RNA? 2. RNA polymerase: Any direction? Why? 3. RNA polymerase: Need a primer? 4. Initiation of RNA synthesis: How to find the right place? Where is the right place? Which DNA strand is the right strand for transcription? 5. Termination of RNA synthesis: where is the right place for termination? 6. Transcription: write down the relative position of promoter position, terminator, start codon, stop codon for a polycistronic mRNA
上泽充通大￥ Shanghai Jiao Tong University IV mRNA Transcription Why do we need a messenger RNA? ·The genetic information needs to be read“one sentence at a time",just like we speak in sentences.Genes are“sentences”in genetic information Protein synthesis takes place away from where chromosome exists No.3 Chen Feng.Shanghai Jiao Tong University
No. 3 Chen Feng, Shanghai Jiao Tong University IV. mRNA Transcription Why do we need a messenger RNA? • The genetic information needs to be read “one sentence at a time”, just like we speak in sentences. Genes are “sentences” in genetic information • Protein synthesis takes place away from where chromosome exists
上泽充通大学 Shanghai Jiao Tong University 7.7 Overview of transcription 7.7.1 RNA polymerase RNA polymerase requires DNA as a template Direction:5'→3'. Do not need primer:RNA polymerase can start chains Triphosphate-containing:The initial nucleotide in an RNA retains 3 phosphate The first base in the rNa is always a purine. No.4 Chen Feng.Shanghai Jiao Tong University
No. 4 Chen Feng, Shanghai Jiao Tong University 7.7 Overview of transcription RNA polymerase requires DNA as a template Direction: 5’ 3’. Do not need primer: RNA polymerase can start chains Triphosphate-containing: The initial nucleotide in an RNA retains 3 phosphate The first base in the RNA is always a purine. 7.7.1 RNA polymerase
上泽克通大学 Shanghai Jiao Tong University Overview of Transcription Transcription(DNA to RNA)is carried out by RNA polymerase RNA polymerase uses DNA as template RNA precursors are ATP,GTP,CTP,and UTP Chain growth is 5'to 3'just like DNA replication No.5 2012 Pearson Education,Inc. Chen Feng.Shanghai Jiao Tong University
No. 5 Chen Feng, Shanghai Jiao Tong University Overview of Transcription Transcription (DNA to RNA) is carried out by RNA polymerase • RNA polymerase uses DNA as template • RNA precursors are ATP, GTP, CTP, and UTP • Chain growth is 5′ to 3′ just like DNA replication © 2012 Pearson Education, Inc
上帝充通大学 Shanghai Jiao Tong University Overview of Transcription Only one of the two strands of DNA are transcribed by RNA polymerase for any gene Genes are present on both strands of DNA,but at different locations RNA polymerase has five different subunits RNA polymerase recognizes DNA sites called promoters No.6 Chen Feng.Shanghai Jiao Tong University
No. 6 Chen Feng, Shanghai Jiao Tong University Only one of the two strands of DNA are transcribed by RNA polymerase for any gene Genes are present on both strands of DNA, but at different locations RNA polymerase has five different subunits RNA polymerase recognizes DNA sites called promoters Overview of Transcription
上帝充通大学 Shanghai Jiao Tong University Overview of Transcription Promoters:site of initiation of transcription Recognized by sigma factor of RNA polymerase Transcription stops at specific sites called transcription terminators Unlike DNA replication,transcription involves smaller units of DNA Often as small as a single gene Allows cell to transcribe different genes at different rates No.7 Chen Feng.Shanghai Jiao Tong University
No. 7 Chen Feng, Shanghai Jiao Tong University Promoters: site of initiation of transcription • Recognized by sigma factor of RNA polymerase Transcription stops at specific sites called transcription terminators Unlike DNA replication, transcription involves smaller units of DNA • Often as small as a single gene • Allows cell to transcribe different genes at different rates Overview of Transcription
Steps in RNA synthesis 1:Initiation Initiate Terminate Promoter The initiation and termination sites are specific nucleotide sequences on region the DNA.初始化位点与终止点为特定序列 5' 3 1 Gene 5 RNA polymerase (core enzyme) Sigma aids in recognition of Sigma factor promoter and initiation site 5 3 3 5 The sigma factor allows RNA polymerase to recognize the initiation site(the promoter'）.启动子的识别
Steps in RNA synthesis 1: Initiation The initiation and termination sites are specific nucleotide sequences on the DNA.初始化位点与终止点为特定序列 The sigma factor allows RNA polymerase to recognize the initiation site (the promoter). 启动子的识别
Steps in RNA synthesis 2:elongation The sigma factor is released Sigma during elongation. 5 3 3 5' Transcription begins; Elongation:RNA polymerase moves down the DNA chain,causing temporary sigma released opening of the double helix..a延长阶段 5 3 3 5 RNA chain 5 growth
Elongation: RNA polymerase moves down the DNA chain, causing temporary opening of the double helix.延长阶段 The sigma factor is released during elongation. Steps in RNA synthesis 2: elongation
Steps in RNA synthesis 3:termination 5 3 3 5 Termination site reached:chain 5 growth stops When a termination site is reached, and the mRNA and polymerase are 5 released. 3 3 5 Release of polymerase 3 and RNA 5 FLASH 2
When a termination site is reached, and the mRNA and polymerase are released. Steps in RNA synthesis 3: termination FLASH 2