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Below are two statements:

Statement I: In an E. coli cell, lac operon activity must be low.
Statement II: Lactose is transported into bacteria by the permease enzyme.

Based on the above statements, select the most appropriate answer.

Option: 1

Statements I and II are both correct

Option: 2

Statements I and II are both incorrect

Option: 3

Statement I is correct but Statement II is incorrect

Option: 4

Statement I is incorrect but Statement II is correct

Answers (1)



  • Without glucose, Lactose serves as an alternate Carbon source. Hence, Statement I is correct.
  • However, Lactose transport into the E. coli cell requires a permease enzyme, which is controlled by the lac operon.
  • Therefore, a low level of lac operon activity is necessary for E.coli cells at all times making Statement II a correct statement. 
  • Three genes make up the lac operon, a polycistronic structural gene:
    • The 'z' code represents β-galactosidase
    • The 'y' code represents Permease
    • The 'a' code represents a Transacetylase
  • Lactose can enter E. coli cells with the Permease enzyme, which increases permeability.
  • Hence, option 1 is the correct answer. 
Posted by

seema garhwal

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