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NEETZoologyMolecular Basis of Inheritance

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): A very low level of expression of the lac operon has to be present in the cell all the time. Reason (R): Lactose cannot enter the cell if permease is completely absent. In the light of the above statements, choose the most appropriate answer from the options given below:

Options

  1. ABoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)
  2. BBoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A)
  3. CAssertion (A) is true but Reason (R) is false
  4. DAssertion (A) is false but Reason (R) is true

Correct answer

A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)

Step-by-step solution

Assertion (A) is true. NCERT states that a very low (basal) level of expression of the lac operon must be present in the cell at all times. Reason (R) is true. Permease, which is the product of the y gene of the lac operon, is required to transport lactose into the cell. Reason (R) correctly explains Assertion (A). If the operon were completely shut off with absolutely zero expression, no permease would be present in the cell membrane. Without permease, lactose (the inducer) could not enter the cell to bind the rep

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