Anticodoncodon

Anticodoncodon is a term used in molecular biology to describe the complementary and antiparallel interaction between the anticodon of transfer RNA (tRNA) and a codon in messenger RNA (mRNA) during translation. The codon is a three-nucleotide sequence in mRNA that specifies a particular amino acid or a stop signal. The tRNA carries the corresponding amino acid and features an anticodon triplet in its anticodon loop that base-pairs with the codon in the ribosome's decoding center.

In canonical pairing, the codon is read 5' to 3' and the anticodon aligns 3' to 5', forming Watson-Crick base pairs (A–U and G–C) with the codon. At the third codon position, wobble base pairing allows nonstandard pairing, often enabling a single tRNA to recognize multiple codons; inosine in the anticodon can pair with A, U, or C.

The anticodon loop of tRNA typically includes nucleotides at positions 34–36, with base modifications helping stabilize pairing and ensure correct recognition. The interaction is coordinated with aminoacyl-tRNA synthetases that attach the appropriate amino acid to the tRNA; while charging largely depends on tRNA identity elements, some synthetases use anticodon identity as well.

Genetic code redundancy means most amino acids are encoded by more than one codon, and anticodon-codon pairing, together with wobble rules, underlies efficient translation. Stop codons are not recognized by tRNAs but by release factors. Anticodoncodon is central to translation fidelity and the evolution of decoding strategies across organisms.