Bacterial Lactose Metabolism and the lac Operon
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Questions and Answers

What is the main function of inducible operons?

  • Fine-tune transcrip=on to match the metabolic needs of the cell
  • Increase glucose sensitivity in bacteria
  • Activate transcrip=on of the operon based on the substrate (correct)
  • Repress metabolic pathways

    • What is the primary role of operons in bacterial genomes?

  • Control protein translation
  • Govern DNA replication
  • Modulate cellular respiration
  • Coordinate transcriptional regulation of genes in the same pathway (correct)

    • Which operon in E.coli is responsible for producing polypeptides needed for lactose utilization?

  • Mal operon
  • Trp operon
  • Glc operon
  • Lac operon (correct)

    • What describes the regulatory region shared by genes in an operon?

    <p>Operator</p> Signup and view all the answers

    How do inducible operons differ from repressible operons?

    <p>Operate through activation by a substrate</p> Signup and view all the answers

    What is the preferred energy source for E.coli?

    <p>Glucose</p> Signup and view all the answers

    What is the most common structural feature of regulatory DNA-binding proteins in bacteria?

    <p>Helix-turn-helix motif</p> Signup and view all the answers

    How do the polypeptides of a regulatory homodimer interact with DNA sequences?

    <p>Each polypeptide interacts with one repeat unit.</p> Signup and view all the answers

    What is the significance of the 'turn' in the helix-turn-helix motif of regulatory DNA-binding proteins?

    <p>It separates a recognition helix and a stabilizing helix.</p> Signup and view all the answers

    What was the outcome of the mutational analysis of the lac operon mutants?

    <p>Continuous transcription of lacZ and lacY genes despite lactose availability</p> Signup and view all the answers

    Which of the following best describes the cons%tu%ve mutants in the lac operon?

    <p>They prevent the transcription of lacZ and lacY genes regardless of lactose availability.</p> Signup and view all the answers

    What is the role of complementation analysis in studying lac operon mutants?

    <p>To assign mutations into different complementation groups</p> Signup and view all the answers

    What compound is the real inducer of the lac operon?

    <p>Allolactose</p> Signup and view all the answers

    What is the function of the lac operon?

    <p>Produce enzymes for lactose metabolism</p> Signup and view all the answers

    Which enzyme is encoded by the lacY gene within the lac operon?

    <p>Lactose permease</p> Signup and view all the answers

    In the lac operon, what is the function of the lac repressor protein?

    <p>Prevents transcription in the absence of glucose</p> Signup and view all the answers

    What happens when lactose is available but glucose is also present in the cell?

    <p>lac repressor binds to the operator</p> Signup and view all the answers

    In a repressible operon, what causes transcription of the operon to be blocked?

    <p>Presence of end product</p> Signup and view all the answers

    When tryptophan is absent in the cell, what happens in the trp operon?

    <p>Transcription of trp operon is induced</p> Signup and view all the answers

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