tRNA–mRNA recognition: Which specific region of a tRNA base-pairs directly with the codon on an mRNA during translation?

Introduction:
Translation accuracy depends on correct codon–anticodon pairing. Transfer RNAs provide the physical link by presenting an anticodon that reads the mRNA codon while carrying its matched amino acid at the acceptor stem. Pinpointing the interacting region clarifies how sequence information is converted into protein sequence.

Given Data / Assumptions:

• tRNA has a cloverleaf secondary structure with an anticodon loop.
• The acceptor stem ends in CCA-3′ where the amino acid is attached.
• Ribosomal decoding occurs at the small subunit's A site.

Concept / Approach:
The anticodon triplet in the tRNA anticodon loop forms Watson–Crick (and some wobble) base pairs with the codon triplet on the mRNA. This interaction ensures that the amino acid attached at the distant acceptor stem matches the mRNA specification via charging specificity and ribosomal selection checkpoints.

Step-by-Step Solution:

Verification / Alternative check:
High-resolution ribosome structures reveal codon–anticodon base pairs and monitoring by 16S/18S rRNA nucleotides in the decoding center, directly confirming the anticodon's role.

Why Other Options Are Wrong:

• Codon: resides on mRNA, not tRNA.
• Amino acid site/5′ end/variable loop: do not base-pair with mRNA codons.

Common Pitfalls:
Confusing the location of the codon (mRNA) with the anticodon (tRNA) or assuming the amino acid side dictates pairing; pairing is nucleic-acid based.

Final Answer:
Anticodon