What occurs during translation elongation?

• A. A site accepts an aminoacyl-tRNA, a peptidyl transferase forms a peptide bond, then the ribosome translocates to continue elongation.
• B. Initiation occurs.
• C. Stop codon recognized triggers release factors.
• D. tRNA is charged by aminoacyl-tRNA synthetase.

Answer: (A)

During translation elongation, the ribosome repeats a cycle that adds one amino acid at a time to the growing chain. The aminoacyl-tRNA binds at the A site, matching the next codon, and the peptidyl transferase enzyme forms a peptide bond between the existing polypeptide on the tRNA in the P site and the new amino acid on the A-site tRNA. After the bond forms, the ribosome translocates along the mRNA, shifting the tRNAs through the sites so the growing chain moves into position for the next round of elongation. This sequence is exactly what happens in elongation, making it the best description.

Initiation happens at the start of translation, not during elongation. A stop codon triggers release factors during termination, not during elongation. Charging tRNA with amino acids by aminoacyl-tRNA synthetase occurs before translation begins, in the cytoplasm, not in the elongation cycle.