Question

Which of the following is(are) INCORRECT in the regulation of the trp operon?

• A. It is an example of a negatively controlled repressible operon
• B. The amino acid Trp inactivates the repressor
• C. The amino acid Trp induces the operon
• D. The repressor binds to the operator in the presence of amino acid Trp

Hint:

The tryptophan operon works on negative feedback: high Trp → repression.

Answer 1

The Correct Option is B, C

Step 1: Understand the trp operon.
The trp operon is a negatively controlled repressible operon. When tryptophan levels are high, tryptophan acts as a corepressor.
Step 2: Evaluate each statement.
(A) Correct — It is indeed a negatively controlled repressible operon.
(B) Incorrect — Tryptophan activates the repressor, not inactivates it.
(C) Incorrect — Tryptophan represses the operon; it does not induce it.
(D) Correct — The Trp–repressor complex binds to operator to stop transcription.
Step 3: Conclusion.
Thus, statements (B) and (C) are incorrect.