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Gene Regulation

Explore the intricate gene regulation mechanisms in bacterial and eukaryotic cells. Understand how transcriptional-level control plays a pivotal role in bacteria while eukaryotes exhibit complex gene regulation across multiple levels. Delve into operons, such as the lacoperon and trp operon, to grasp the nuances of inducible, repressible, and constitutive genes. Discover the unique aspects of gene regulation in eukaryotic cells, including promoter efficiency variations and gene amplification. Uncover the significance of differential mRNA processing in tissue-specific gene expression.

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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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