Prokaryotic Gene Regulation Overview
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Questions and Answers

What roles do A, B, and C play in the example of the repressilator?

  • A and C activate expression while B represses it.
  • A represses expression, B expresses, and C represses A. (correct)
  • B and C both repress A expression.
  • All three genes are expressed in the cycle.

    • What is transcription attenuation primarily associated with?

  • Increased RNA polymerase activity.
  • Premature termination of transcription. (correct)
  • Activation of transcription.
  • Enhanced gene expression in eukaryotes.

    • What function do riboswitches serve in gene expression regulation?

  • They enhance transcription regardless of small molecules.
  • They are involved in protein degradation.
  • They change conformation when bound to a small molecule. (correct)
  • They facilitate splicing of RNA.

    • How does low guanine levels affect transcription of purine biosynthetic genes?

    <p>Transcription is enhanced.</p> Signup and view all the answers

    What type of organism utilizes riboswitches to regulate gene expression?

    <p>Prokaryotes, plants and some fungi.</p> Signup and view all the answers

    What kind of feedback loops can be associated with transcriptional circuits?

    <p>Circadian gene regulation and feedback loops.</p> Signup and view all the answers

    Which bases are considered purines in DNA/RNA?

    <p>Adenine and Guanine.</p> Signup and view all the answers

    What can interfere with RNA polymerase during transcription attenuation?

    <p>Regulatory proteins binding to RNA.</p> Signup and view all the answers

    What role does the lambda repressor protein play under good growth conditions?

    <p>It turns off Cro and activates itself.</p> Signup and view all the answers

    What is a characteristic feature of positive feedback loops in transcriptional circuits?

    <p>They create cell memory.</p> Signup and view all the answers

    What is the function of feed-forward loops in biological systems?

    <p>To measure the duration of a signal.</p> Signup and view all the answers

    In eukaryotic cells, what is the outcome of combining various regulatory circuits?

    <p>Creation of complex regulatory networks.</p> Signup and view all the answers

    What is the key concept behind synthetic biology as demonstrated by the Repressilator?

    <p>Constructing circuits to study biological behavior.</p> Signup and view all the answers

    What type of feedback mechanism does the Repressilator rely on?

    <p>Delayed negative feedback.</p> Signup and view all the answers

    What interaction leads to oscillations in the Repressilator circuit?

    <p>Delayed negative feedback among multiple repressors.</p> Signup and view all the answers

    Which of the following best describes the relationship between prophage state and lytic state in lambda phage?

    <p>The lytic state is favored during high cellular stress.</p> Signup and view all the answers

    What is the main function of the tryptophan repressor in prokaryotic gene regulation?

    <p>To prevent transcription by binding to DNA</p> Signup and view all the answers

    Which mechanism allows the NtrC protein to activate transcription from a distance?

    <p>DNA looping</p> Signup and view all the answers

    What role do the lambda repressor and Cro proteins play in bacteriophage lambda?

    <p>They repress each other's synthesis to control the viral life cycle.</p> Signup and view all the answers

    In positive regulation during prokaryotic transcription, what is the primary role of the activator protein?

    <p>To recruit RNA polymerase to the promoter</p> Signup and view all the answers

    What is the significance of a helix-turn-helix DNA binding motif in prokaryotic gene regulation?

    <p>It allows proteins to bind to major grooves of DNA.</p> Signup and view all the answers

    What is the primary effect of transcription attenuation on RNA molecules?

    <p>It leads to premature termination.</p> Signup and view all the answers

    How do regulatory elements influence transcription in prokaryotes?

    <p>They can be located far from the transcription start site.</p> Signup and view all the answers

    Which statement describes the state of the bacteriophage lambda during the lytic phase?

    <p>Cro protein allows extensive transcription of bacteriophage DNA.</p> Signup and view all the answers

    What triggers the switch between prophage and lytic states in bacteriophage lambda?

    <p>Environmental stress conditions</p> Signup and view all the answers

    What is the role of riboswitches in gene control?

    <p>To regulate gene expression in response to metabolite levels</p> Signup and view all the answers

    In which way do negative feedback loops function in gene expression?

    <p>They prevent overexpression of genes.</p> Signup and view all the answers

    During the prophage state, what is the role of the lambda repressor protein?

    <p>To inhibit the synthesis of Cro and promote its own synthesis</p> Signup and view all the answers

    What determines the specific binding of the tryptophan repressor to DNA?

    <p>The concentration of tryptophan in the cell</p> Signup and view all the answers

    Why are gene regulatory elements important in prokaryotic gene expression?

    <p>They enable precise control over gene expression levels.</p> Signup and view all the answers

    Study Notes

    Prokaryotic Gene Regulation

    • Most common DNA binding motif: helix-turn-helix
    • Tryptophan repressor protein contains a helix-turn-helix binding motif
    • Tryptophan binding induces conformational change
    • Tryptophan repressor binds to the major groove of the DNA double helix

    Regulation

    • Negative Regulation: RNA polymerase competes with repressor proteins for promoter binding sites
    • Positive Regulation: Activator proteins recruit RNA polymerase to the promoter and activate transcription
    • Regulatory elements are typically close to the transcriptional start site in prokaryotes
    • Regulatory elements can also be found far upstream of the gene
    • Regulatory elements can be found downstream of the gene
    • Regulatory elements can be found within the gene (introns)

    NtrC

    • NtrC is a transcriptional activator
    • DNA looping allows NtrC to directly interact with RNA polymerase
    • DNA looping activates transcription from a distance

    Bacteriophage Lambda

    • Virus that infects bacterial cells
    • Two gene regulatory proteins initiate switching between prophage and lytic pathways: lambda repressor protein (cI) and Cro protein
    • lambda repressor and Cro repress each other’s synthesis

    Prophage State

    • Lambda Repressor occupies the operator
    • Lambda repressor blocks synthesis of Cro
    • Lambda repressor activates its own synthesis
    • Most bacteriophage DNA is not transcribed

    Lytic State

    • Cro occupies the operator
    • Cro blocks synthesis of lambda repressor
    • Cro activates its own synthesis
    • Most bacteriophage DNA is transcribed
    • DNA replication occurs
    • New bacteriophage is packaged
    • Host cell lysis occurs and bacteriophage is released

    Prophage to Lytic State Switching

    • Host response to DNA damage causes the switch to the lytic state
    • The switch inactivates the repressor

    Positive Feedback Loop

    • Under good growth conditions, lambda repressor protein turns off Cro and activates itself in a positive feedback loop
    • This loop maintains the prophage state

    Transcriptional Circuits

    • Control various biological processes

    Positive Feedback Loops

    • Create cell memory

    Feed-Forward Loops

    • Measure signal duration

    • Both A and B are required for transcription of Z

    • Brief input: B does not accumulate, Z is not transcribed

    • Prolonged input: B accumulates, Z is transcribed

    Synthetic Biology

    • Scientists construct artificial circuits to examine their behavior in cells

    The Repressilator

    • Simple gene oscillator using a delayed negative feedback circuit
    • Repressors: Lac, Tet, Lambda
    • Predicted: delayed negative feedback gives rise to oscillations
    • Repressor genes were introduced into bacterial cells and expression was observed

    Transcriptional Attenuation

    • Premature termination of transcription
    • RNA adopts a structure that interferes with RNA polymerase
    • Regulatory proteins can bind to RNA and interfere with attenuation

    Riboswitches

    • Short RNA sequences that change conformation when bound by a small molecule
    • Regulate gene expression
    • Examples: Prokaryotic riboswitches that regulate purine biosynthesis

    Purine Biosynthesis

    • Bases in DNA/RNA include purines (A,G) and pyrimidines (C, U, T)
    • Low guanine levels: transcription of purine biosynthetic genes is on

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    Related Documents

    BIO230 Lecture 3: Prokaryotic Transcriptional Regulation Continued (Fall 2024) PDF

    Description

    This quiz explores key concepts of prokaryotic gene regulation, including DNA binding motifs, repressor and activator proteins, and the role of regulatory elements. Understand the mechanisms involved in transcriptional activation and repression, with a focus on the interplay between different proteins and DNA structure.

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