Anticodon
An anticodon is a three-nucleotide sequence located in the anticodon loop of a transfer RNA (tRNA) molecule that is complementary and antiparallel to a specific mRNA codon during translation. Base pairing between the codon and anticodon — following Watson-Crick rules (A-U and G-C) and sometimes wobble base pairing at the third position — ensures that the correct amino acid is added to the growing polypeptide chain. Each tRNA carries a specific amino acid at its 3' CCA end that corresponds to its anticodon, making tRNA the physical link between the nucleotide and amino acid languages of the cell.
Codon–Anticodon Base Pairing Examples
| mRNA Codon (5'→3') | tRNA Anticodon (3'→5') | Amino Acid | Wobble Position |
|---|---|---|---|
| AUG | UAC | Methionine | G:C (Watson-Crick) |
| UUU | AAA | Phenylalanine | U:A (Watson-Crick) |
| GGU | CCA | Glycine | U:A (Watson-Crick) |
| GGC | CCG | Glycine | C:G (Watson-Crick) |
| CGA | GCU | Arginine | A:U (Watson-Crick) |
| GGG | CCC | Glycine | G:C (Watson-Crick) |
Interactive Tools
Brilliant.org: Translation and tRNA
Interactive problems on anticodon recognition and wobble pairing
Open Tool
Wikimedia Commons, CC BY-SA
Related Terms
Codon
A codon is a sequence of three consecutive nucleotides (a triplet) in mRNA that specifies a particular amino acid or signals the start or stop of protein synthesis. With four possible bases (A, U, G, C) at each of three positions, there are 4³ = 64 possible codons, which encode 20 standard amino acids plus three stop codons and one start codon (AUG, which codes for methionine). The redundancy of the genetic code — where multiple codons can specify the same amino acid — is called degeneracy and provides robustness against point mutations.
Transfer RNA (tRNA)
Transfer RNA (tRNA) is a small non-coding RNA molecule, typically 73–95 nucleotides long, that acts as a physical adaptor during translation by carrying a specific amino acid to the ribosome and recognising the corresponding mRNA codon via its anticodon loop. Each tRNA has a characteristic cloverleaf secondary structure that folds into an L-shaped three-dimensional conformation; the 3' CCA end accepts the amino acid (charged by aminoacyl-tRNA synthetase), while the anticodon loop base-pairs with the mRNA codon in the ribosomal A site. There are at least 61 functional tRNA species in cells (matching all sense codons), and their accurate aminoacylation is essential for translational fidelity.
Translation (biology)
Translation is the process by which a ribosome decodes the nucleotide sequence of a messenger RNA (mRNA) and synthesizes the corresponding sequence of amino acids to produce a polypeptide chain. It occurs in three phases — initiation, elongation, and termination — and takes place at ribosomes in the cytoplasm of both prokaryotes and eukaryotes. The genetic code, read in triplets called codons, determines which amino acid is incorporated at each step, with transfer RNA (tRNA) molecules acting as adaptors between the mRNA codons and the amino acids.
Formed from the prefix anti- (Greek, meaning "against" or "opposite") and codon. The term was introduced in the early 1960s as the complementary counterpart to the mRNA codon, indicating that the two sequences pair in an antiparallel, complementary fashion.