The trp operon is known to operate by both negative repressible regulation of operator and attenuation. which of the following statements does not support the reason as to why dual control exists to regulate the operon?
a. attenuation and repression allow the cell to more sensitively respond to the tryptophan level.
b. combined mechanism provides a much finer tuning of tryptophan synthesis regulation.
c. the repression alone is never complete, and some transcription can be initiated.
d. repression responds to the cellular levels of tryptophan, while attenuation responds to the number of trna charged with tryptophan.
e. it is most likely due to the fact that the attenuation is the evolutionary relic, which by accident has remained.