What is tRNA charging and which enzyme performs it?

• A. Attachment of amino acid to tRNA by aminoacyl-tRNA synthetase.
• B. Synthesis of tRNA from precursor RNA.
• C. Removal of amino acid from tRNA.
• D. Degradation of tRNA by ribonuclease.

Answer: (A)

Charging tRNA is attaching an amino acid to the tRNA molecule, a step carried out by aminoacyl-tRNA synthetases. Each amino acid has its own synthetase, and the process begins with activation of the amino acid by ATP to form aminoacyl-AMP. The activated amino acid is then transferred to the 3’ end of the tRNA, producing aminoacyl-tRNA. This charge is essential so the ribosome can insert the correct amino acid into the growing polypeptide chain according to the mRNA codon. The enzyme also helps ensure fidelity by recognizing the correct tRNA and sometimes editing mischarged amino acids.

The other ideas describe different processes: creating tRNA from precursor RNA is transcription and processing of tRNA, not charging. Removing the amino acid is deacylation, not charging. Degrading tRNA is degradation, not charging.