NEET 2019 Odisha · BiologyPrevious Year Question
Which of the following statements about the lac-operon is correct?
Answer: (A) Gene is constitutively expressed. Correct Answer (A): Gene is constitutively expressed The regulatory gene is expressed constitutively (always on) to make the repressor.
- A.Gene is constitutively expressed✓
- B.Lactose activates the repressor to bind to the operator
- C.Genes , , and share a single common promoter
- D.Galactose can act as an inducer of the lac operon
Correct Answer
(A) Gene is constitutively expressed
Solution & Explanation
Correct Answer (A): Gene is constitutively expressed The regulatory gene is expressed constitutively (always on) to make the repressor. Lactose (its isomer allolactose), not galactose, is the inducer and it INACTIVATES the repressor (so the repressor binds operator only in the ABSENCE of lactose). The structural genes , , share a promoter, but gene has its own promoter. So only statement (1) is correct.
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