Question

Question 4 1.5 pts The presence of absence of tryptophan determines whether the genes in the trp operon code for the enzymes necessary for tryptophan synthesis. True OFalse

Answer 1

• Trp operon controls trp production by attenuation process as per the presence or absence of tryptophan.
• Trp operon Representations:
• R = Repressor gene
• Rn Repressor cannot bind tryptophan, transcription occurs even in presence of Tryptophan.
• R- = Repressor cannot bind to the operator
• O= Operator
• O- = operator cannot bind repressor protein, transcription occurs even in presence of Tryptophan.
• Trp L = leader sequence, Attenuator sequence present. att = Attenuator
• L- or att- = deletion of the attenuator sequence, so repressor cannot bind, transcription will occur.
• P = Promoter
• P- = a deletion of the trp operon promoter
• trpE- and trpC- = non-functional protein products produced.
• Co-repressor activates the repressor.
• In repressible system, like Trp operon, tryptophan act as co-repressor.
• Tryptophan act as co-repressor for its own biosynthesis.
• When tryptophan is present, the cell does not require more tryptophan.
• Tryptophan binds to the repressor (encoded by R gene) to activate it and binds to operator to prevent transcription of the gene required for tryptophan biosynthesis.
• Thus, in presence of tryptophan, trp operon is switched off.

Answer:True