The trp operon of e. coli controls expression of five enzymes that are involved in the biosynthesis of the amino acid tryptophan. a trp repressor protein (trpr) binds to the trp operator to prevent transcription when tryptophan is present. when would the tryptophan synthesis enzymes be made if the trpr gene was mutated?

If the trpR gene is mutated, then the tryptophan synthesis enzymes would be synthetized in PRESENCE or ABSENCE of tryptophan.

An operon is a fragment of DNA containing several adjacent genes that are transcribed under the control of a single promoter.

An operator is a site in which a regulatory molecule binds into an operon and thus acts as an on/off switch for transcription.

In Escherichia coli, the trp repressor is a protein homodimer that controls transcription of the tryptophan biosynthetic pathway.

The tryptophan amino acid binds to the trp repressor, thereby changing its tridimensional conformation and converting it into its active form.

The trp repressor binds to DNA upstream of the start of transcription and thus prevents access by RNA polymerase.

In conclusion, if the trpR gene is mutated, then the tryptophan synthesis enzymes would be synthetized in PRESENCE or ABSENCE of tryptophan.

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Tryptophan synthesis enzymes be made during low level of cellular tryptophan.

Explanation:

Tryptophan operon  contain 3 regulatory gene(trpR,trpP and trpO) and 5 structural genes(trpE,trpD,trpC,trpB and trpA) .trpR encodes the repressor protein that interacts with tryptophan present in the media and then the tryptophan repressor complex binds to the operator region to block the transcription of the structural genes of tryptophan operon.

   Here tryptophan acting as a corepresor.During mutation of trpR gene tryptophan biosynthesis enzymes will be synthesized only when the cellular tryptophan level remains very low.

explanation:

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b is the correct answer