Translation termination occurs when a stop codon is encountered at which ribosomal site?

Translation termination occurs when a stop codon is encountered at which ribosomal site?

• A. A site
• B. E site
• C. P site
• D. None

Answer: (A)

Termination happens when a stop codon sits in the A site of the ribosome. That position is where the codon is read and where release factors recognize the stop signal. When a stop codon is in the A site, release factors bind and trigger hydrolysis of the bond between the polypeptide and the tRNA in the P site, releasing the completed protein. The ribosome then dissociates from the mRNA, aided by recycling factors. The E site is just where deacylated tRNA exits, not where termination is signaled, and the P site is where the growing polypeptide-tRNA resides during elongation. So termination is triggered by the stop codon being in the A site.

Termination happens when a stop codon sits in the A site of the ribosome. That position is where the codon is read and where release factors recognize the stop signal. When a stop codon is in the A site, release factors bind and trigger hydrolysis of the bond between the polypeptide and the tRNA in the P site, releasing the completed protein. The ribosome then dissociates from the mRNA, aided by recycling factors. The E site is just where deacylated tRNA exits, not where termination is signaled, and the P site is where the growing polypeptide-tRNA resides during elongation. So termination is triggered by the stop codon being in the A site.