The Trp operon is a coordinately regulated group of genes (trpA-trpE) that are required for tryptophan biosynthesis in E. coli. Based on the figure above, which of the following correctly describes the regulation of the Trp operon?

• In the absence of tryptophan, the repressor is active and binds to the Trp operator, preventing RNA polymerase from transcribing the operon.

• In the presence of tryptophan, the repressor is active and binds to the Trp operator, preventing RNA polymerase from transcribing the operon.

• In the absence of tryptophan, the trpR gene is inactive, preventing the production of the repressor that blocks expression of the operon

• In the presence of tryptophan, the trpR gene is inactive, preventing the production of the repressor that blocks expression of the operon

 

Transcribed Image Text:

RNA Polymerase Promoter Operator trpE trpD trpC trpB trpA DNA P trpR R Active Repressor 5-- trpR MRNA R Inactive Repressor Active Repressor R = Repressor molecule T= Tryptophan molecule Pg = Promoter for the trpR gene trpR = Repressor gene Operator Binding site for repressor molecule RNA Polymerase Promoter Operator trpE trpD trpC trpB trpA DNA P trpR R Active Repressor 5-- trpR MRNA R Inactive Repressor Active Repressor R = Repressor molecule T= Tryptophan molecule Pg = Promoter for the trpR gene trpR = Repressor gene Operator Binding site for repressor molecule

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