Quiz  /  NEET MCQ on Lac Operon

  • 1. 
    Lac operon is an example of

  • only positive regulation
  • only negative regulation
  • both positive and negative regulation
  • sometimes positive sometimes negative

  • 2. 
    In the presence of lactose, how long does it take for the lac operon to be expressed?

  • when lactose equals glucose concentration
  • when glucose is more than lactose concentration
  • as long as lactose is more than glucose concentration
  • as long as lactose is more than galactose concentration

  • 3. 
    Which of these acts as an inducer of the lac operon?

  • Allolactose
  • Lactose
  • Galactose
  • Glucose

  • 4. 
    The sequence of the structural genes in the lac operon is

  • lacA-lacZ-lacY
  • lacZ-lacY-lacA
  • lacZ-lacA-lacY
  • lacA-lacY-lacZ

  • 5. 
    Regulation of the lac operon can be envisioned as regulation of enzyme synthesis by its

  • lactose
  • substrate
  • carbohydrates
  • all of the above

  • 6. 
    Lac Operon will be turned on when

  • Lactose is less than glucose
  • Lactose is less in the medium
  • Lactose is more than glucose
  • Glucose is enough in the medium

  • 7. 
    In a cell as per the Operon Concept, the regulator gene governs the chemical reactions by

  • Inhibiting the substrate in the reaction
  • Inhibiting migration of mRNA into cytoplasm
  • mRNA transcription inhibited
  • Enzyme-reaction inactivation

  • 8. 
    In Lac-operon, the gene product of LacA gene is

  • Beta-galactoside permease
  • Beta-galactoside transacetylase
  • Beta-galactosidase
  • Beta-galactoside isomerase

  • 9. 
    This condition in lac operon facilitates the condition of lac genes being transcribed at high levels

  • low glucose, high lactose
  • low glucose, low lactose
  • high glucose, high lactose
  • high glucose, low lactose

  • 10. 
    The correct option regarding the lac operon in Ecoli from the following is

  • Lac operon is switched on in the absence of lactose
  • Lac repressor binds to the lac promoter
  • β-galactosidase is the only enzyme produced in large quantities when lac operon is turned on
  • lac operon messenger RNA is a polycistronic mRNA
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