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Gene Regulation

Gene Regulation. Gene regulation in bacteria and eukaryotes Bacterial cells Grow rapidly and have short life span Transcriptional-level control best Eukaryote cells Long life span Gene regulation complex Transcriptional-level control dominates, but other levels important, also.

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Gene Regulation

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  1. Gene Regulation

  2. Gene regulation in bacteria and eukaryotes • Bacterial cells • Grow rapidly and have short life span • Transcriptional-level control best • Eukaryote cells • Long life span • Gene regulation complex • Transcriptional-level control dominates, but other levels important, also

  3. Gene regulation in bacteria • Most organized into operons • Gene complex plus linked DNA • Each has single promoter region upstream • Operator regulates transcriptional-level control of operon • When repressor protein binds to operator, it prevents transcription • Binds specifically to the lac operator sequence

  4. The lacoperon

  5. Genetic and biochemical characterization of the lac operon

  6. Inducible, repressible, and constitutive genes • Inducible operon, such as lac operon, normally turned off • Repressible operon, such as the trp operon, normally turned on • Constitutive genes • Neither inducible nor repressible • Active at all times

  7. The trp operon

  8. Negative regulators inhibit transcription • Repressible and inducible operons • When repressor protein binds to the operator, transcription is turned off • Positive regulators stimulate transcription • Some inducible operons • Regulated by activator proteins

  9. Positivecontrol ofthe lacoperon

  10. A regulon

  11. Gene regulation in eukaryotic cells • Not organized into operons • Gene regulation occurs at the levels of • Transcription • mRNA processing • Translation • The protein product

  12. Eukaryotic promoters vary in efficiency, depending on UPEs • Promoter consists of • RNA polymerase-binding site • Upstream promoter elements (UPEs) • Number and types of UPEs determine efficiency • Inducible eukaryotic genes controlled by enhancers

  13. Regulationof transcriptionin eukaryotes

  14. Regulatory proteins

  15. Stimulationof transcriptionby an enhancer

  16. Chromosome organization may affect gene expression • Genes are inactivated by changes in chromosome structure • DNA methylation is mechanism that perpetuates gene inactivation • Multiple copies of some genes present in one chromosome • Gene amplification

  17. Differential mRNA processing • Cells in each tissue produce own version of mRNA • For example, different forms of troponin, a protein that regulates muscle contraction, produced in different muscle tissue

  18. Differential mRNA processing

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