7) When is the lactose operon likely to be transcribed? a) When there is more gl

Question

7) When is the lactose operon likely to be transcribed? a) When there is more glucose in the cell than lactose b) When there is more lactose in the cell than glucose c) When there is lactose but no glucose in the cell d) When the repressor protein is present. Page 3 8) Transcription of the structural genes in an inducible operon a) is likely to occur all the time b) occurs when the pathway's substrate is present. c) starts when the pathway's product is present. d) stops when the pathway's product is present e) does not produce enzymes 9) What is the function of the operator locus of the lactose operon? a) To terminate production of repressor molecules b) To identify the substrate c) To initiate the production of mRNA d) To control the binding of RNA polymerase to the operator region. 10) For a repressible operon to be transcribed, which of the following must be true? a) RNA polymerase and the active repressor must be present b) RNA polymerase must bind to the promoter and the repressor must be inactive c) RNA polymerase cannot be present and the repressor must be inactive d) RNA polymerase must not occupy the promoter and the repressor must be inactive 11) A mutation that renders the regulatory gene of a repressible operon nonfunctional would result in a) continuous transcription of the structural genes b) continuous synthesis of an inducer c) accumulation of large quantities of a substrate for other structural genes d) irreversible binding of the repressor to the promoter

Explanation / Answer

7. b

Lac operon is active when there is high lactose and low glucose.

8. b

Example is lac operon in which genes are transcribed when lactose is present.

9. d

The operator binds repressor and prevents binding of RNA polymerase to promoter.

10. b, RNA polymerase must bind to the promoter and the repressor must be inactive.

11. a, continous transcription of the structural genes.

This is called as constitutive expression as repressor is not present.

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