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GATE 2024 BT – Question 51

Genetics, Cellular and Molecular Biology · Molecular Biology: Replication, transcription, splicing, translation, non-coding and micro RNA, RNA interference, DNA damage and repair · 2 marks · Multiple select

Which of the following conditions induce(s) the expression of β-galactosidase gene in the lac operon?

  1. Absence of glucose
  2. Absence of lactose
  3. Presence of glucose
  4. Presence of lactose

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Correct answer: (A) Absence of glucose; (D) Presence of lactose

Explanation

Lactose (allolactose) removes the repressor, and low glucose gives high cAMP so CAP activates the operon. Both conditions are needed for full expression.

Official GATE 2024 answer key: https://gate2026.iitg.ac.in/doc/download/2024/BTFinalAnswerKey.pdf