Question

A deletion mutation in the leader sequence of the trp operon removes the two tryptophan codons that are involved in attenuation. Predict the effect of this mutation on the expression of the trpstructural genes in E. coli cells grown in media that lacks tryptophan.(a) The trp structural genes will be expressed in order to synthesize tryptophan.(b) The trp structural genes will have decreased expression because the mRNA will adopt the terminator configuration.(c) The repressor protein R will be bound to the operator locus O.

Answer 1

Answer:

Option a) The trp structural genes will be expressed in order to synthesize tryptophan

Explanation:

The operon tryptophan is in charge of the expression of genes related with tryptophane production.  This occurs in absence of tryptophane.

Being tryptophane present, this interacts with the repressor protein R and occupy the operator locus, blocking the transcription process.

In absence of tryptophane, transcription occurs but the produced amount of this amino acid affects negatively its production, as attenuaton responds to concentrations of tARN charged with tryptophane.

In this case, the attenuation region is not present (by deletion) and there is not additional repression or negative regulation.

As a result, there is no tryptohane to block transcription, and there's not attenuation region.  Then structural genes would be transcripted in order to synthesize tryptophan