What is the start codon?

AUG is the standard start codon. It signals the ribosome to begin translation and also codes for methionine, so most proteins begin with a methionine residue that is often removed afterward. A few alternative start codons exist in some organisms.

Which codons are stop codons?

UAA, UAG, and UGA are the three stop codons in the standard genetic code. They do not encode an amino acid; instead they signal release factors to terminate translation and free the finished polypeptide from the ribosome.

Why do multiple codons code for the same amino acid?

The genetic code is degenerate: most amino acids are specified by two to six codons. This redundancy, concentrated in the third codon position (the wobble position), buffers against many point mutations that would otherwise change the protein.

What is the difference between DNA and RNA codons?

RNA codons use uracil (U) where DNA uses thymine (T). Codon tables are written for messenger RNA, so this tool uses U. To convert a DNA coding strand, replace every T with U before looking up the codon.

What does the wobble position mean?

The third base of a codon often pairs loosely with the tRNA anticodon, a flexibility called wobble. It explains why changing the third base frequently encodes the same amino acid, and why a single tRNA can read several codons.

Genetic Codon Table Reference

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The genetic code maps each three-base RNA codon to an amino acid (or a stop signal). This reference translates any of the 64 codons using the standard genetic code and highlights the start and stop codons.

How it works

Messenger RNA is read in non-overlapping triplets called codons. Each of the three positions can be A, U, G, or C, giving 4 × 4 × 4 = 64 possible codons. Of these:

AUG is the start codon and also encodes methionine.
UAA, UAG, and UGA are stop codons and encode no amino acid.
The remaining 60 codons encode the other amino acids, with most amino acids specified by several synonymous codons.

This tool looks up a codon in the standard code table and returns the amino acid, or flags start/stop.

Tips and example

AUG → Methionine (Met, M) and marks the start of translation.
The code is degenerate: UUU and UUC both encode phenylalanine.
For DNA, replace T with U first — the coding strand ATG becomes the codon AUG.