What is the role of release factors in translation termination?

• A. They assemble ribosomal subunits.
• B. They recognize stop codons and catalyze peptidyl-tRNA hydrolysis, releasing the polypeptide.
• C. They deliver aminoacyl-tRNA to the A site.
• D. They unwind mRNA secondary structures during translation.

Answer: (B)

Translation termination hinges on release factors recognizing stop codons and triggering the release of the newly made polypeptide. When a stop codon sits in the A site, release factors bind there and catalyze the hydrolysis of the bond between the polypeptide and the tRNA, freeing the completed protein. In bacteria, different release factors recognize the specific stop codons, while in eukaryotes a single factor recognizes all stop codons and coordinates ribosome recycling afterward. The other roles listed belong to different stages: assembling ribosomal subunits occurs during initiation, delivering aminoacyl-tRNA to the A site happens during elongation, and unwinding mRNA structures is part of helicase activity during scanning and translation.