Quiz  /  Operon Class 12 MCQ Questions With Answers

  • 1. 
    Inducible negative control is when when the gene is transcribed by the ____ of a specific molecule

  • presence
  • absence

  • 2. 
    Which of the following describes the type of pathway that a repressible operon controls?

  • anabolic pathway
  • catabolic pathway

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

  • presence
  • absence

  • 4. 
    What is the name of the stretch of DNA where RNA polymerase binds?

  • operator
  • promoter
  • enhancer
  • origin

  • 5. 
    Which of the following describes an operon that is active and becomes inactivated by a molecule binding to the repressor?

  • inducible operon
  • repressible operon

  • 6. 
    The "on/off" switch for an operon is called the

  • promoter
  • repressor
  • operator
  • gene

  • 7. 
    Lac operon can be found in

  • E. coli
  • lactose
  • human colon
  • glucose

  • 8. 
    If the DNA code reads CCAATTGG then the tRNA code would read ____________

  • CCAATTGG
  • CCAAUUGG
  • GGUUAACC
  • GGTTAACC

  • 9. 
    In the top picture the operon is

  • on
  • off

  • 10. 
    All of the following is true about pre-mRNA that is produced in eukaryotes EXCEPT

  • Consist of intron and exon
  • Carry genetic information for specific protein synthesis
  • Will be used as template in translation process
  • Synthesized in nucleus during transcription

  • 11. 
    Introns are

  • Noncoding sequence of mRNA
  • Coding sequence of mRNA
  • Complex of molecules that cut out the introns and splice together the exons
  • Involves the removal of introns, fusing of the exons, and the addition of a 5’ cap and a Poly A tail to mRNA

  • 12. 
    What happen to lac operon in the absence of lactose?

  • lac operon is switched off
  • lac operon is active
  • repressor protein bind to promoter
  • RNA polymerase binds to operator

  • 13. 
    If a promoter was being deleted in lac operon, what would be the effect towards lac operon in the absence of lactose?

  • RNA polymerase can transcribe the structural genes
  • Enzymes are being produced
  • Repressor protein will change its shape
  • RNA polymerase cannot bind to lac operon

  • 14. 
    What is the role of the ribosome in protein synthesis?

  • it is where mRNA synthesis occurs
  • it is where DNA synthesis occurs
  • it is where protein synthesis occurs
  • it is where gene synthesis occurs

  • 15. 
    The lac Z gene codes for:

  • permease
  • beta-galactosidase
  • repressor of lac operon
  • transacetylase

  • 16. 
    During transcription _________

  • DNA is made complimentary to RNA
  • RNA is made complimentary to DNA
  • a protein is made from the RNA base sequence
  • a protein is made from the DNA base sequence

  • 17. 
    An operon consists of all of the following except:

  • operator
  • regulatory gene
  • promoter
  • genes of the operon

  • 18. 
    Once transcription has been completed, which of the following is NOT necessary for protein synthesis to occur?

  • tRNA
  • ribosomes
  • mRNA
  • DNA

  • 19. 
    In the absence of glucose, the lac operon system is activated when the person consumes the following, EXCEPT

  • soy milk
  • yoghurt
  • cream cheese
  • milkshake

  • 20. 
    RNA is synthesized on a DNA template in a process called ______, which utilizes the enzyme _______

  • translation, RNA polymerase
  • transcription, DNA polymerase
  • transcription, RNA polymerase
  • replication, DNA polymerase

  • 21. 
    Which of the following is active in the absence of lactose?

  • lacI
  • lacZ
  • lacY
  • lacA

  • 22. 
    Given the following DNA strand, which of the following is its complementary mRNA? 3’ G G A C T G A T T 5’

  • 3’ C C U G A C U A A 5’
  • 5’ C C U G A C U A A 3’
  • 5’ G G A C T G A T T 3’
  • 3’ T T A G T C A G G 5’

  • 23. 
    What is the enzyme that detoxifies other molecules entering the cell via the permease?

  • β-galactosidase
  • β-galactoside primase
  • β-galactoside permease
  • β-galactoside transacetylase

  • 24. 
    Which of the following conditions leads to maximal expression of the lac operon?

  • lactose present, glucose absent
  • lactose present, glucose present
  • lactose absent, glucose absent
  • lactose absent, glucose present

  • 25. 
    Functioning unit of DNA containing a cluster of genes under the control of a single regulatory signal or promoter is termed as

  • Operon
  • Operator
  • Lac
  • Repressor protein
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