Lecture 3.1: Bacterial Genes Regulation - FINISH!!!

Genes are the instructions to make proteins (Slide 4)

  • How do genes regulate protein synthesis?

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Cell Express different genes at different rates (Slides 5)

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Levels of Regulation In Gene Expression (Slide 6)

  • Gene expression in bacteria can be regulated at 3 levels:

    • Transcriptional Control: RNA production

    • Translation Control: protein production

    • Post-translational control: protein modification → protein loses function

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Genes are organized into operons (Slide 7)

  • Operon:

    • Promoter: where gene transcription starts

    • Operator: where repressor or activator binds

    • Genes: sequence for protein production

  • Regulatory Gene: regulates operator or promoter binding, which in turn regulates gene transcription → controls the promoter or operator

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Lecture Question 1: The Advantage of Operons (Slide 8)

  • what are the advantages of organizing genes as operons?

    • efficiency →a single promoter / operator for a series of genes regulation

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Transcription Regulator Proteins → Introduction (Slide 9)

  • Most Common type of gene regulation

  • transcriptional regulators are proteins that bind to the operator or promoter DNA sequence

  • 2 classes of regulators:

    • repressor (repress gene transcription)

    • activators (activates gene transcription)

Positive Regulation vs. Negative Regulation (Slide 10)

  • positive regulation involves activator which binds to operator to begin transcription

  • negative regulation involves repressor which to operator to block transcription

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Gene regulation can depend on carbon source (Slide 11)

  • genes are turned on when needed

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Gene Regulation and Operon

3 Operon models → how cells regulate genes (Slide 13)

  • Operon Models:

    • lac operon: lactose uptake and breakdown

    • trp operon: tryptophan biosynthesis

    • ara operon: arabinose processing

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How can lactose control gene in bacteria? (Slide 14)

  • Lactose: disaccharide composed of galactose and glucose

  • in bacteria, B-galactosidase enzyme is responsible to breakdown the bond in lactose

  • for the lac operon, lactose availability regulates lacZ, lacY, and lacA genes

  • lacZ encodes for B-galactoside, which is responsible in cleaving lactose

    • the point is to get glucos to for the cell

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Lecture Question 2: DNA region that encodes for proteins (Slide 15)

  • which parts of the DNA region shown in the diagram encode for proteins?

    A. promoter, operator, lacZ, lacY, lazA

    B. lacI, lacZ, lacY, lacA

    C. lacI, promoter, operator

    D. opertaor, lacZ, lacY, lacA

    • only the genes encode for proteins

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Negative Control of Lactose (lac) operon (Slide 16)

  • B-galactosidase, peremase, and transacetylase are produced when lactose is present

  • lac I encodes repressor which binds to operator and block transcription

  • with lactose present, repressor binds to lactose instead of operator

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How Lactose affecting lac operon (Slide 17)

  • in the absence of lactose, the lac repressor binds the operator, and transcription is blocked.

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  • in the presence of lactose, the lac repressor is realsed from the operator, and transcription proceeds at a slow rate