Codon to Amino Acid Translator

Type three letters, get the three-letter abbreviation of the amino acid. Before the lookup the script uppercases the input and replaces every T with U, so DNA codons behave the same way: ATG and AUG both return Met (start), TGA and UGA both return STOP. The embedded table holds all 64 codons of the standard genetic code, NCBI translation table 1 — 61 sense codons plus the three stops UAA, UAG and UGA. Anything outside those 64 combinations returns an invalid-codon message rather than a guess. One codon per lookup, refreshed on every keystroke.

Almost all of the redundancy sits in the third base. GCN in any of its four forms codes alanine, CGN codes arginine, and the same four-fold family pattern holds for proline (CCN), threonine (ACN), valine (GUN), glycine (GGN) and the UCN block of serine, where the third letter changes nothing. Three amino acids get six codons each, split across two blocks that are not adjacent in the table: leucine (UUA, UUG plus the four CUN), serine (the four UCN plus AGU and AGC) and arginine (the four CGN plus AGA and AGG). At the other extreme, methionine and tryptophan have a single codon apiece, which makes AUG and UGG brittle positions — a single substitution in UGG produces UGA, a stop.

What the page leaves out matters as much as what it does. It handles one codon at a time: no reading frames, no ORF scanning, no reverse complement, no single-letter code and no full amino acid name. The table is the standard one and nothing else. Under the vertebrate mitochondrial code (NCBI table 2) UGA reads as tryptophan instead of stop, AUA reads as methionine instead of isoleucine, and AGA and AGG are stop codons — in every one of those cases this page will silently report the nuclear value. Input is not trimmed either, so pasting AUG with a trailing space returns invalid codon. And the start label rides along with AUG even when the AUG is an internal methionine.