Question

multiple choice question

in what way can a riboswitch directly regulate translation?

by blocking the promoter site
by changing the shape of the mrna
by forming an attenuator site
by forming a termination codon site

Explanation:

Analyze the mechanism of riboswitches in translation regulation

A riboswitch is a regulatory segment of a messenger RNA (mRNA) molecule that binds a specific small molecule ligand. This binding directly alters the secondary structure (shape) of the mRNA.

Evaluate the given options

• By blocking the promoter site: Promoters are DNA sequences involved in transcription initiation, not translation.
• By changing the shape of the mRNA: Ligand binding to a riboswitch alters the mRNA's folding, which can sequester or expose the Shine-Dalgarno sequence (ribosome binding site), directly regulating translation initiation.
• By forming an attenuator site: Attenuation is a mechanism that regulates transcription termination, not direct translation.
• By forming a termination codon site: Riboswitches do not dynamically create or destroy stop codon sequences.

Determine the correct choice

The direct structural change of the mRNA upon ligand binding is the primary mechanism by which a riboswitch controls translation.

Answer:

• (A) By blocking the promoter site
• (B) By changing the shape of the mRNA (Correct answer)
• (C) By forming an attenuator site
• (D) By forming a termination codon site