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

Explanation:

The trp operon is a repressible operon that is turned off when tryptophan (trp) is present in the environment. The determining factor for the transcription of its structural genes is the availability of tryptophan. When tryptophan is abundant, it binds to the trp repressor, activating it to bind to the operator and prevent transcription. Option A is incorrect as the quantity of trp repressor protein doesn't determine transcription (the repressor's activity depends on tryptophan). Option B is incorrect as RNA polymerase binding to the promoter is a general step, but the trp operon's regulation is about repression by tryptophan. Option D is incorrect as the location of the regulatory gene isn't the determining factor. Option E is incorrect as other operons' activity isn't related to trp operon's transcription.

Answer:

C. the availability of tryptophan in the environment