In the context of the trp operon, what happens when tryptophan levels are high?

In the context of the trp operon, what happens when tryptophan levels are high?

• A. The repressor is deactivated
• B. RNA polymerase is blocked
• C. The repressor is activated
• D. The promoter becomes inactive

Answer: (C)

In the context of the trp operon, when tryptophan levels are high, the repressor is activated. This occurs because tryptophan acts as a corepressor. When excess tryptophan is present, it binds to the inactive repressor protein, causing a conformational change that enables the repressor to attach to the operator region of the operon. This attachment blocks RNA polymerase from transcribing the genes necessary for tryptophan biosynthesis, effectively turning off the operon. This mechanism allows the cell to conserve energy and resources by preventing the synthesis of unnecessary enzymes when an adequate amount of tryptophan is already available. The activation of the repressor in response to high tryptophan levels illustrates a classic example of negative feedback regulation in gene expression.

In the context of the trp operon, when tryptophan levels are high, the repressor is activated. This occurs because tryptophan acts as a corepressor. When excess tryptophan is present, it binds to the inactive repressor protein, causing a conformational change that enables the repressor to attach to the operator region of the operon. This attachment blocks RNA polymerase from transcribing the genes necessary for tryptophan biosynthesis, effectively turning off the operon.

This mechanism allows the cell to conserve energy and resources by preventing the synthesis of unnecessary enzymes when an adequate amount of tryptophan is already available. The activation of the repressor in response to high tryptophan levels illustrates a classic example of negative feedback regulation in gene expression.