Question

select the correct answer
what is the determining factor for the transcription of structural genes of the trp operon?
a. the quantity of trp repressor protein made by the regulatory gene trpr
b. the ability of rna polymerase to bind to the promoter region
c. the availability of tryptophan in the environment
d. the location of a regulatory gene with reference to the other regions of the operon
e. the activity of the other operons present in bacteria
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Explanation:

The trp operon is a repressible operon. The regulatory gene trpR produces the trp repressor protein. The quantity of this repressor protein determines whether it can bind to the operator (a part of the operon) to regulate the transcription of structural genes. When there is enough tryptophan (corepressor), it binds to the repressor, activating it to bind to the operator and block transcription. When tryptophan is scarce, the repressor is inactive and cannot bind, allowing transcription.

Answer:

A. the quantity of trp repressor protein made by the regulatory gene trpR