In molecular genetics, the three-base sequence on transfer RNA that pairs with a messenger RNA codon is called an anticodon.
During translation, a transfer-RNA molecule carries a particular amino acid to a ribosome. Its anticodon binds to a complementary codon on messenger RNA through base pairing. This matching helps the ribosome place amino acids in the order encoded by the gene.
The codon and anticodon are complementary, but they are read in opposite directions because nucleic-acid strands are antiparallel. The transfer RNA’s other end carries the amino acid, so the anticodon connects the nucleotide language of messenger RNA with the amino-acid language of proteins.
An anticodon is different from a codon. Codons are found on messenger RNA and provide the instructions, whereas anticodons are found on transfer RNA and help interpret those instructions. Special pairing rules at some positions, known as wobble, allow one transfer RNA to recognize more than one codon.