Define antisense RNA, and describe how it affects the translation of a complementary mRNA. Why is it more advantageous to the organism to stop translation initiation than to inactivate or destroy the gene product after it is produced?

Both attenuation of the trp operon in E. coli and riboswitches in B. subtilis rely on changes in the secondary structure of the leader regions of mRNA to regulate gene expression. Compare and contrast the specific mechanisms in these two types of regulation with those involving short noncoding RNAs (sRNAs).

Microbiologists describe the processes of transcription and translation as 'coupled' in bacteria. This term indicates that a bacterial mRNA can be undergoing transcription at the same moment it is also undergoing translation.

How is coupling of transcription and translation possible in bacteria?

The bacterial insertion sequence IS10 uses antisense RNA to regulate translation of the mRNA that produces the enzyme transposase, which is required for insertion sequence transposition. Transcription of the antisense RNA gene is controlled by P_OUT, which is more than 10 times more efficient at transcription than the P_IN promoter, which controls transposase gene transcription.

If a mutation of P_IN eliminates its ability to function in transcription, what is the likely effect on the transposition of IS10?

What is a riboswitch? Describe the riboswitch mechanism that regulates transcription of the thi operon in B. subtilus. What parallels can you see between this mechanism and the regulation of transcription of the trp operon in E. coli?

What is the major difference between the mechanism involved in attenuation and riboswitches and the mechanism involved in the regulation of the lactose operon?

Riboswitches are made up of what type of molecule?