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Regulation of Gene Expression

Regulation of Gene Expression. In Prokaryotes & Eukaryotes. Regulation of Gene Expression by Bacteria. Transcription. Regulation of metabolic pathways. Bacterial control of gene expression. Operon : cluster of related genes with on/off switch Three Parts:

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Regulation of Gene Expression

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  1. Regulation of Gene Expression In Prokaryotes & Eukaryotes

  2. Regulation of Gene Expression by Bacteria Transcription

  3. Regulation of metabolic pathways

  4. Bacterial control of gene expression Operon: cluster of related genes with on/off switch Three Parts: • Promoter – where RNA polymerase attaches • Operator – “on/off”, controls access of RNA poly • Genes – code for related enzymes in a pathway

  5. Regulatory gene: produces repressorprotein that binds to operator to block RNA polymerase

  6. Repressible Operon (ON  OFF) Inducible Operon (OFF  ON)

  7. Repressible Operon • Normally ON • Anabolic (build organic molecules) • Organic molecule product acts as co-repressor binds to repressor to activate it • Operon is turned OFF • Eg. trpoperon

  8. trp operon

  9. Inducible Operon • Normally OFF • Catabolic (break down food for energy) • Repressor is active inducerbinds to and inactivates repressor • Operon is turned ON • Eg. lacoperon

  10. lac operon

  11. Regulation of Gene Expression by Eukaryotes Occurs at many stages during the process of gene transcription, post transcription, translation and post translation

  12. Typical human cell: only 20% of genes expressed at any given time • Different cell types (with identical genomes) turn on different genes to carry out specific functions • Differences between cell types is due to differential gene expression

  13. Eukaryotic gene expression regulated at different stages

  14. Chromatin Structure: • Tightly bound DNA less accessible for transcription • DNA methylation: methyl groups added to DNA; tightly packed;  transcription • Histone acetylation: acetyl groups added to histones; loosened;  transcription

  15. Epigenetic Inheritance • Modifications on chromatin can be passed on to future generations • Unlike DNA mutations, these changes to chromatin can be reversed (de-methylation of DNA) • Explains differences between identical twins

  16. Transcription Initiation: • Control elements bind transcription factors • Enhances gene expression

  17. Transcription Initiation Complex Enhancerregions bound to promoter region by activators

  18. Regulation of mRNA: • micro RNAs (miRNAs) and small interfering RNAs (siRNAs) can bind to mRNA and degrade it or block translation

  19. Eukaryotic Gene Expression Summary:

  20. Eukaryotic Gene Expression Summary cont.

  21. Eukaryotic Gene Expression Summary cont.

  22. Destinations for Newly Translated Polypeptides:

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