Genetic regulation in prokaryotes can involve alterations in RNA secondary structure.What phenomenon occurs in the trp operon that involves such alterations?
A) transcription
B) capping
C) polyadenylation of the 3′ end of the mRNAs
D) intron processing
E) attenuation

Question

Quizplus · Accepted Answer

The phenomenon that occurs in the trp operon that involves alterations in RNA secondary structure is attenuation. Attenuation is a regulatory mechanism found in some bacterial operons that involves the formation of different RNA secondary structures which affect the rate of transcription elongation. In the trp operon, attenuation is regulated by the availability of tryptophan, which acts as a co-repressor. When tryptophan levels are high, it binds to the repressor protein (TrpR) and allows it to bind to the trp operator, repressing transcription. When tryptophan levels are low, the ribosome stalls at a specific sequence (trp leader peptide) of the mRNA and forms an RNA hairpin loop, which promotes the formation of a terminator hairpin, prematurely terminating transcription. Thus, by altering RNA secondary structure, attenuation allows the cell to regulate gene expression in response to changing environmental conditions.

Genetic Regulation in Prokaryotes Can Involve Alterations in RNA Secondary