In translation, what happens when a ribosome reaches a stop codon in the mRNA?

• A. The ribosome shifts into a new reading frame (frameshift) and continues elongation from the next codon.
• B. A tRNA carrying a specialized amino acid binds to the stop codon and adds that amino acid to the growing polypeptide chain.
• C. The small ribosomal subunit remains bound to the mRNA and continues scanning until it finds the next start codon to begin translation again immediately.
• D. A release factor binds in the A site, catalyzing hydrolysis of the peptidyl-tRNA bond so the completed polypeptide is released and the ribosome dissociates.

Answer: (D)