Question

15. Which correctly describes the functional significance of the RNA structures?

Select one:

a. Local base-parings are the key causes of unique RNA 3-D structures.

b. RNAs have various 3-D structures for their biological functions.

c. Changes in RNA structures are employed in controls of transcription and/or translation.

d. The termination hairpins or the riboswitches are the actual examples.

e. All of these

Answer 1

E: All of these.

Like proteins, most RNAs can fold spontaneously into complex three-dimensional shapes. Therefore, the function of both proteins and RNAs depends on the three-dimensional structure and dynamics. For example, the primary sequence of a tRNA molecule can fold into a clover leaf like secondary structure by the pairing of the complementary bases in the primary sequence. The clover leaf structure further folds into a 3D structure in the form of letter L, which is the actual structure of all tRNAs. This structure is needed for a tRNA for its recognition by its synthetase enzyme, for its amino acylation, recognition by translation initiation/elongation factors, entry into the active centers of the ribosome, pairing with its codon peptide bonding and so on. The same is true for most RNAS like the snRNAs involved in splicing. Rearrangements in the 3D structure of snRNAs is important in splicing,, control of transcription initiation and termination and also in translation control. The 3D structure adopted by the growing RNA chain in bacteria is important in both Rho dependent and independent transcription termination. Similarly RNA structures are involved in the control of attenuator mediated transcription regulation of trp operon of E. coli and in the functioning of many regulatory RNAs of bacteria.