Quiz  /  Operon Class 9 MCQ Questions With Answers

  • 1. 
    What is an operon?

  • a part of a ribsome
  • a part of a Rna
  • a unit made up of linked genes that code for proteins needed to do a specific task
  • needed for dna replication

  • 2. 
    Which of the following describes the function of the operator in the operon?

  • site of repressor binding for on/off switch
  • site of RNA polymerase binding for transcription
  • site of promoter binding for RNA synthesis
  • site of inducer binding for activation of pathway

  • 3. 
    Inducible negative control is when when the gene is transcribed by the ____ of a specific molecule

  • presence
  • absence

  • 4. 
    In the lac operon, the allolactose binds to the repressor. Which of the following is the term used to describe this molecule?

  • inducer
  • corepressor
  • enhancer
  • CAP

  • 5. 
    The lac operon genes only become expressed if:

  • lactose binds to the repressor
  • glucose binds to the repressor
  • lactose binds to the operator
  • the repressor binds to the operator

  • 6. 
    Which of the following describes the type of pathway that a repressible operon controls?

  • anabolic pathway
  • catabolic pathway

  • 7. 
    How can a person's muscle cells have the same exact DNA sequences as their nerve cells even though the look and perform completely different?

  • The two different cells become mutated
  • The proteins expressed in each cell are different
  • They actually have different DNA in the two types of cells.
  • The genome of the different cells changes

  • 8. 
    Which of the following describes an operon that is inactive and becomes activated by a molecule binding to the repressor?

  • inducible operon
  • repressible operon

  • 9. 
    What is the role of operons in prokaryote gene expression?

  • It makes the genes prokaryotes be turned on
  • It accounts for the regulation of gene activity in response to the needs of the cells
  • To make DNA for the gene
  • To make the gene turn of and off

  • 10. 
    The trp operon is an example of an repressible operon. Which of the following describes the process that occurs when tryptophan is present?

  • The tryptophan binds to the repressor which inactivates it and the repressor binds to the operator to turn translation off.
  • The tryptophan binds to the repressor which activates it and the repressor releases from the operator to turn translation off.
  • The tryptophan binds to the repressor which inactivates it and the repressor releases from the operator to turn translation off.
  • The tryptophan binds to the repressor which activates it and the repressor binds to the operator to turn translation off.

  • 11. 
    Operons are found in the cells of which of the following types of organisms?

  • prokaryotes (bacteria)
  • eukaryotes (plant and animals)
  • animals only
  • viruses

  • 12. 
    Which of the following describes the function of the promoter in the operon?

  • site of repressor binding for on/off switch
  • site of RNA polymerase binding for transcription
  • site of operator binding for RNA synthesis
  • site of inducer binding for activation of pathway

  • 13. 
    The lac operon is an example of an inducible operon. Which of the following describes the process that occurs when lactose is present?

  • The lactose binds to the repressor which inactivates it and the repressor binds to the operator to turn translation on.
  • The lactose binds to the repressor which activates it and the repressor releases from the operator to turn translation on.
  • The lactose binds to the repressor which inactivates it and the repressor releases from the operator to turn translation on.
  • The lactose binds to the repressor which activates it and the repressor binds to the operator to turn translation on.

  • 14. 
    A protein that binds to the operator and blocks the RNA polymerase

  • regulator
  • repressor
  • activator
  • corepressor

  • 15. 
    Repressible negative control is when when the gene is transcribed by the ____ of a specific molecule

  • presence
  • absence

  • 16. 
    What is the name of the stretch of DNA where RNA polymerase binds?

  • operator
  • promoter
  • enhancer
  • origin

  • 17. 
    What type of operon is the trp (tryptophan) operon?

  • inducible
  • repressible
  • positive control
  • promoible

  • 18. 
    In the trp operon, the tryptophan binds to the repressor. Which of the following is the term used to describe this molecule?

  • inducer
  • corepressor
  • enhancer
  • CAP

  • 19. 
    Which of the following describes an operon that is active and becomes inactivated by a molecule binding to the repressor?

  • inducible operon
  • repressible operon

  • 20. 
    Which of the following describes the type of pathway that an inducible operon controls?

  • anabolic pathway
  • catabolic pathway

  • 21. 
    The "on/off" switch for an operon is called the

  • promoter
  • repressor
  • operator
  • gene

  • 22. 
    In the lac operon model the genes within the operon will be expressed if:

  • lactose is absent in the cell
  • glucose is present in the cell
  • lactose is present in the cell
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