Question

When tryptophan is present, what happens in trp operon?

• A. Repressor becomes inactive.
• B. Repressor is unable to bind to the operator.
• C. Transcription of structural genes occur.
• D. Repressor is able to bind to operator.

Answer 1

The correct option is D Repressor is able to bind to operator.

• The tryptophan (trp) operon system is a type of repressible operon system.
  
• When tryptophan is present, it binds the trp repressor and induces a conformational change in that protein, enabling it to bind the trp operator and prevent transcription (operon is repressed). Hence there will be no transcription of structural genes.
  

So the correct answer is option D.