Question

During attenuation, when tryptophan levels are high, the _______ stem loop forms and transcription _______ the trpL gene

A)2-3 , ends just past
B) 3-4 end, ends just past
C) 1-2 , continues beyond
D) 3-4 continues beyond

Answer 1

When tryptophan levels are high, the 3-4 stem loop forms, which causes transcription to terminate just past the trpL gene.

Step-by-step explanation:

During attenuation, when tryptophan levels are high, the 3-4 stem loop forms and transcription ends just past the trpL gene. This is because the presence of abundant tryptophan allows the leader peptide encoded by trpL to be translated, which leads to the formation of the terminator loop between regions 3 and 4. As a result, transcription is terminated right after the leader sequence, preventing further transcription of the structural genes of the trp operon.