BCH4024 - Long Lecture 53

BCH4024 - Long Lecture 53 - Lecture 56: Transcriptional...

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1 DNA RNA Protein Replication Transcription Translation Lecture 56: Transcriptional regulation and DNA binding Today’s lecture: Chapter 28a Download from http://lss.at.ufl.edu prokaryotic transcription and regulation Protein recognition and binding to DNA Review session: 1-3 on Friday, 4/24 Office hours: 1-3 pm on Thursday ¾ Regulation is mainly at the transcription level ¾ Not all DNA is transcribed in a given cell (less than 50% even in prokaryotes) ¾ E. coli only produces the enzymes needed for lactose utilization when lactose is in the growth media ¾ François Jacob and Jacques Monod noted mutants of E. coli which had errors in regulating the production of β -galactosidase and proposed a macromolecular repressor regulated the level of enzyme production ¾ They hypothesized the repressor binds to a specific operator sequence in DNA (1961) ¾ This is known as the operon model Regulation of protein concentration and function
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2 ¾ The promoter is where the RNA polymerase binds initially contains consensus sequences of 6 nucleotides each at 35 and 10 bases before the transcription start site ¾ These promoters can vary in groups (different σ proteins). Different promoters can be favored by changing the σ protein in RNA polymerase ¾ Some genes are constitutively transcribed (housekeeping genes) and their level of transcription is dependent on promoter homology ¾ Inducible genes are transcribed based on need ¾ Transcription and translation can be regulated over several orders of magnitude Æ induction and repression Transcriptional regulation happens via several mechanisms σ 32 σ 70 Repression and induction of transcription
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3 Prokaryotic cells have polycistronic mRNA which contains the sequences for more than one enzyme in a particular metabolic pathway Æ operon Transcribed together The lac operon Binding of allolactose or IPTG releases the DNA
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This note was uploaded on 03/15/2010 for the course BCH 4024 taught by Professor Allison during the Spring '08 term at University of Florida.

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BCH4024 - Long Lecture 53 - Lecture 56: Transcriptional...

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