Which Statement Is TRUE of the Attenuation Mechanism Used to Regulate

Multiple Choice

Which statement is TRUE of the attenuation mechanism used to regulate the tryptophan biosynthetic operon in E. coli?

A) Attenuation is the only mechanism used to regulate the trp operon.
B) One of the enzymes in the Trp biosynthetic pathway binds to the mRNA and blocks translation when tryptophan levels are high.
C) The leader peptide plays a direct role in causing RNA polymerase to attenuate transcription.
D) Trp codons in the leader peptide gene allow the system to respond to tryptophan levels in the cell.
E) When tryptophan levels are low, the trp operon transcripts are attenuated (halted) before the operon's structural genes are transcribed.