Select the two correct statements out of the four (a-d) given below about lac operon:
(a) Glucose or galactose

Question

Select the two correct statements out of the four (a-d) given below about lac operon:
(a) Glucose or galactose may bind with the repressor and inactivate it.
(b) In the absence of lactose, the repressor binds with the operator region.
(c) The z-gene codes for permease.
(d) This was elucidated by Francois Jacob and Jacques Monod.

Accepted Answer

According to the NCERT text: 
1. Statement (a) is incorrect: Glucose or galactose cannot act as inducers; lactose or allolactose binds to the repressor to inactivate it .
2. Statement (b) is correct: In the absence of lactose (inducer), the repressor protein binds to the operator region of the operon and prevents RNA polymerase from transcribing the operon .
3. Statement (c) is incorrect: The z-gene codes for beta-galactosidase, while the y-gene codes for permease .
4. Statement (d) is correct: The lac operon was elucidated by Francois Jacob and Jacque Monod .
Therefore, statements (b) and (d) are correct.

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