GeneExpression

Why Regulate Gene Expression?Response to changing developmental or environmental conditionsSave…timeenergyraw materials

Prokaryotic RegulationFeedback Inhibition Product inhibits

enzyme function

Regulation of transcription Product inhibits

enzyme production

Drug CompanyDrug CompanyResearch andDevelopment

Research andDevelopment DistributionDistributionTestingTesting ProductionProduction

MGMTMGMT

Operon RegulationInducible

Default off Repressor active

Turned on when substrate is present

Repressor inactive

Repressible

Default on Repressor inactive

Turned off when product is present

Repressor active

Inducible OperonDefault: OFF

1 2 3P ORGRNAPoly

Substrate AbsentRepressor protein binds to operatorOperon blockedNo substrate-catabolizing enzymes produced

Substrate PresentSubstrate inactivates repressor proteinOperon transcribedEnzymes produced

Lac Operon

Trp Operon

Repressible OperonDefault: ON

1 2 3P ORGRNAPoly

Product AbsentRepressor protein inactiveOperon transcribedProduct-anabolizing enzymes produced

Product PresentProduct activates repressor proteinOperon blockedNo enzymes produced

Inducible, Repressible, Both, or Neither?1. The Lac operon2. Regulatory gene codes for repressor protein3. Operon expressed (ON) by default4. Substrate inactivates repressor protein5. Product binds to RNA polymerase6. Product activates repressor protein7. Repressor protein status changes when bound by particles8. Enzymes deactivate repressor protein9. The Trp operon10. Operon blocked (OFF) by default11. Active repressor protein blocks transcription12. Repressor is created in an active state

Inducible, Repressible, Both, or Neither?1. The Lac operon I2. Regulatory gene codes for repressor protein B3. Operon expressed (ON) by default R4. Substrate inactivates repressor protein I5. Product binds to RNA polymerase N6. Product activates repressor protein R7. Repressor protein status changes when bound by particles B8. Enzymes deactivate repressor protein N9. The Trp operon R10. Operon blocked (OFF) by default I11. Active repressor protein blocks transcription B12. Repressor is created in an active state I

Tend to have 10x the genes of prokaryotesExpression is controlled at multiple points

EukaryoticRegulation

Chromatin Modification

EuchromatinHeterochromatin

Chromatin ModificationMethylation

Attachment of methyl groups to cytosine

Histone Acetylation Attachment of acetyl groups to histones Loosens grip of histones on DNA

Alternative Splicing

Post-transcriptional Regulation

Protein Degradation

Review QuestionsUse no more than 1 word for each answer.1. What type of organic molecule is a histone?2. What is the structural difference between

heterochromatin and euchromatin?3. What does a proteasome do?