RNA functionality: Which class of RNA molecules is aminoacylated (covalently linked to an amino acid) for use in protein synthesis?

Introduction:
Each major RNA type has a distinct role in gene expression. Only one class—transfer RNA (tRNA)—is directly charged with amino acids and serves as the adaptor that translates the nucleotide code into the amino acid sequence of proteins. Recognizing tRNA's unique aminoacylation is a core concept in translation biology.

Given Data / Assumptions:

• Aminoacyl–tRNA synthetases attach specific amino acids to matched tRNAs.
• mRNA provides codon templates; rRNA contributes catalytic and structural functions.
• hnRNA is the pre-mRNA precursor in eukaryotes; snRNA participates in splicing.

Concept / Approach:
tRNA molecules possess an acceptor stem ending in CCA-3′ where amino acids are attached via an ester linkage. The anticodon loop allows base pairing with mRNA codons, linking codon identity to the correct amino acid. High specificity of aminoacyl–tRNA synthetases enforces translational fidelity by proofreading both amino acid and tRNA selection.

Step-by-Step Solution:

Verification / Alternative check:
Biochemical charging assays (e.g., with radiolabeled amino acids) and structural studies confirm ester-linked amino acids on tRNAs, not on mRNA or rRNA.

Why Other Options Are Wrong:

• mRNA: template only; not aminoacylated.
• rRNA: catalytic/structural roles in ribosome; no aminoacyl linkage.
• hnRNA/snRNA: nuclear processing RNAs; not part of the amino acid adaptor system.

Common Pitfalls:
Confusing tRNA charging with peptide bond formation or thinking rRNA is the charged adaptor because the ribosome catalyzes peptide bond formation.

Final Answer:
tRNA