Practice question

Attenuation operates during transcription elongation, at regulatory decision point 162 bases downstream of initiation within leader sequence. RNA polymerase remains competent for termination versus readthrough depending on nascent RNA folding influenced by ribosome position on transcript. Unlike repressor control affecting initiation frequency, attenuation determines whether already initiated polymerase aborts prematurely before coding regions. Mechanism requires concurrent translation of leader simultaneous with transcription, positioning ribosome to influence RNA secondary structure dynamically. Thus modality represents elongation-phase regulation that fine-tunes expression tenfold beyond repression effects acting at initiation site under high tryptophan.