Which enzyme attaches the correct amino acid to its tRNA?

Which enzyme attaches the correct amino acid to its tRNA?

• A. DNA polymerase
• B. RNA polymerase
• C. Ligase
• D. Aminoacyl-tRNA synthetase

Answer: (D)

Charging tRNA with the correct amino acid is carried out by aminoacyl-tRNA synthetases. Each amino acid has its own synthetase that recognizes both the amino acid and the corresponding tRNA, using specific features on the tRNA to ensure the right pairing. The enzyme activates the amino acid with ATP to form an aminoacyl-AMP intermediate, then transfers the amino acid to the 3' end of the tRNA, producing aminoacyl-tRNA ready for translation. This step is crucial because the ribosome relies on the attached amino acid to match the codon, so mistakes here would misincorporate amino acids into the growing protein. Many synthetases also have proofreading to remove any mischarged tRNAs, further preserving fidelity. In contrast, DNA polymerase copies DNA, RNA polymerase synthesizes RNA, and ligase seals nicks in the backbone; none of these attach amino acids to tRNA.

Charging tRNA with the correct amino acid is carried out by aminoacyl-tRNA synthetases. Each amino acid has its own synthetase that recognizes both the amino acid and the corresponding tRNA, using specific features on the tRNA to ensure the right pairing. The enzyme activates the amino acid with ATP to form an aminoacyl-AMP intermediate, then transfers the amino acid to the 3' end of the tRNA, producing aminoacyl-tRNA ready for translation. This step is crucial because the ribosome relies on the attached amino acid to match the codon, so mistakes here would misincorporate amino acids into the growing protein. Many synthetases also have proofreading to remove any mischarged tRNAs, further preserving fidelity. In contrast, DNA polymerase copies DNA, RNA polymerase synthesizes RNA, and ligase seals nicks in the backbone; none of these attach amino acids to tRNA.