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Regulation of gene expression in prokaryotes

Regulation of gene expression in prokaryotes. Katalin Kiss Dept. of Medical Biology 12.11. 2007. Gene expression in prokaryotes. Types of expression: Constitutive expression (eg. genes of glucose utilizing enzymes) Regulated expression induction (eg. genes of catabolic enzymes)

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Regulation of gene expression in prokaryotes

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  1. Regulation of gene expression in prokaryotes Katalin Kiss Dept. of Medical Biology 12.11. 2007.

  2. Gene expression in prokaryotes • Types of expression: • Constitutive expression (eg. genes of glucose utilizing enzymes) • Regulated expression • induction (eg. genes of catabolic enzymes) • repression (eg. genes of biosynthetic enzymes) • Significance of regulation: adaption to changes in enviroment (eg. nutrient supply), „feedback” • Level of regulation during gene expression: mostly transcription (activity of RNA polymerase) is regulated • Mechanism of regulation: operon model

  3. Operon model Francois Jacob and Jacques Monod (Nobel-prize 1965.): Study of E.coli bacterium Regulation of gene expression at the level of transcription Operon theory

  4. Operon Components: • Regulated genes = structural genes (transcribed as a polycystronic mRNA) • Promoter • Operator Types: • Inducible • Repressible

  5. Regulatory elements of operon • DNA sequences = „cis-acting elements” (operator, promoter) • Regulatory proteins = „trans-acting elements” (activator, repressor) • Effectors (inducer, corepressor)

  6. Lactose operon (lac operon)

  7. RNA polymerase

  8. lactose

  9. CAP

  10. Regulatory elements of Lactose operon (Lac operon) • Cis-acting elements: operator, promoter • Regulatory proteins: Lac-repressor and CAP • Effectors: lactose and cAMP = inducers

  11. Triptophan operon (Trp operon)

  12. Triptophan operon (Trp operon) Alberts Fig. 7-34

  13. Attenuation of Triptophan operon (Trp operon)

  14. Regulatory elements of Tryptophan operon (Trp operon) • Cis-acting elements: operator, promoter, • attenuator • Regulatory proteins: Trp-repressor • Effectors: trp= korepresszor

  15. Animations of Lac operon and Trp operon on the web • http://highered.mcgraw-hill.com/olc/dl/120080/bio27.swf • http://www.dnatube.com/view_video.php?viewkey=712c49d51a18a32b39f0

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