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Chapter 18. 0. Microbial Models: The Genetics of Viruses and Bacteria. 0.

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Chapter 18

Chapter 18

0

Microbial Models: The Genetics of Viruses and Bacteria


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  • A researcher lyses a cell that contains nucleic acid molecules and capsid units of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. Which of the following would be expected to occur?

    • The plants would develop some but not all of the symptoms of the TMV infection.

    • The plants would develop symptoms typically produced by viroids.

    • The plants would develop the typical symptoms of TMV infection.

    • The plants would not show any disease symptoms.

    • The plants would become infected, but the sap from these plants would be unable to infect other plants.


  • A mutation that inactivates the regulator gene of a repressible operon in an E. coli cell would result in

    • continuous transcription of the structural gene controlled by that regulator.

    • complete inhibition of transcription of the structural gene controlled by that regulator.

    • irreversible binding of the repressor to the operator.

    • inactivation of RNA polymerase.

    • both B and C.


  • A mutation that makes the regulatory gene of an inducible operon nonfunctional would result in

    • continuous transcription of the operon's genes.

    • reduced transcription of the operon's genes.

    • accumulation of large quantities of a substrate for the catabolic pathway controlled by the operon.

    • irreversible binding of the repressor to the promoter.

    • overproduction of cAMP receptor protein.


  • A mutation that renders nonfunctional the product of a regulatory gene for an inducible operon would result in *

    • continuous transcription of the genes of the operon.

    • complete blocking of the attachment of RNA polymerase to the promoter.

    • irreversible binding of the repressor to the operator.

    • no difference in transcription rate when an activator protein was present.

    • negative control of transcription.


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