What happens when levels of tryptophan are low?

When levels of tryptophan are low, the cell initiates several regulatory processes to ensure that tryptophan production can increase. In particular, the transcription of structural genes involved in the synthesis of tryptophan can proceed. This is due to the fact that when tryptophan is scarce, it cannot act as a co-repressor for the repressor protein that regulates the operon responsible for its biosynthesis. As a result, the repressor does not bind effectively to the operator region of the DNA, allowing RNA polymerase to access the promoter and initiate transcription of the genes that encode enzymes necessary for tryptophan production.

This mechanism is indicative of a feedback system that allows the organism to respond to changes in nutrient availability. When tryptophan levels are adequate, tryptophan binds to the repressor, enhancing its affinity for the operator and effectively halting transcription. Conversely, when tryptophan levels drop, this feedback inhibition is lifted, enabling transcription to occur and facilitating the synthesis of tryptophan.

The other choices do not accurately represent the cellular response to low tryptophan levels, focusing instead on processes that would not occur until the repressor is activated or tryptoph