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Chapter 16 Control of Gene Expression. Topics to discuss. DNA binding proteins Prokaryotic gene regulation Eukaryotic gene regulation. 6 groups of DNA-binding regulatory proteins have been identified. Prokaryotic Gene Regulation. Operons Operons provide coordinate expression.
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Topics to discuss • DNA binding proteins • Prokaryotic gene regulation • Eukaryotic gene regulation
6 groups of DNA-binding regulatory proteins have been identified
Operons • Operons provide coordinate expression
Now let’s look at 2 groups of operons • Negative inducible operons • Negative repressible operons
Negative inducible operon INDUCIBLE
Now let’s look at 2 specific operons • The Lactose operon • The Tryptophan operon
Francois Jacob and Jacques Monod 1961 • Studied lactose metabolism in prokayotes
1. Disaccharide 2. Monosaccharide Lactose Glucose Sources of prokaryotic energy
Lac Operon and Proposed Arrangement with control I gene I P O Z Y A Not technically part of the “operon”
Lactose Metabolism Requires Coordination of all these genes!
Lactose Metabolism Requires Coordination of all these genes!
Lac Operon and Proposed Arrangement with control I gene I P O Z Y A Not technically part of the “operon”
Overview of: Mutational Analysis of the lac operon3-24p. Lab manua
No Lactose - 1 + 2 3 4 5 6 7 8 9
Question: what happens when both lactose and glucose are present together in the same cell?
Need to understand this reaction Adenylyl cyclase ATP Cyclic AMP + catabolite activator protein Glucose may inhibit this enzyme
The promoter needs to be in an ideal conformation for RNA polymerase.
Trypthophan Operon • 5 genes involved in the synthesis of the amino acid trypthophan
Do eukaryotes show coordinate gene regulation? Yes, the same response element may be found in related genes.
Changes in Chromatin structure and eukaryotic gene regulation • DNase hypersensitivity • Histone acetylation • DNA methylation
For Your Information Next 4 slides
Experimental tests on the repressor: • I+ cells synthesize full levels of the lac enzymes only in the presence of an inducer • I- mutations NO DNA BINDING ACTIVITY, TRANSCRIPTION OCCURS EVEN IN ABSENCE OF INDUCER! • Is mutation NO LACTOSE BINDING ACTIVITY but has DNA BINDING ACTIVITY. NO TRANSCRIPTION EVEN WITH INDUCER! • Oc mutation: constitutive activity
Oc= constitutive operator, notice how it affects transcription.