Codon Table (Genetic Code) Chart & Quiz

Flashcard quiz

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Which amino acid (or Stop) does this codon encode?

Each codon and answer choice is picked locally in your browser.

Genetic code chart

RNA (U)DNA (T)

All 64 codons of the standard genetic code (NCBI translation table 1). Read the first base down the left, the second across the top, and the third down the right of each block. The start codon AUG is outlined and the three stop codons are shaded grey.

Standard genetic code: first base (rows), second base (columns), third base (inner rows), and the amino acid each codon encodes.
1st	U	C	A	G	3rd
U	UUUPhe · F	UCUSer · S	UAUTyr · Y	UGUCys · C	U
	UUCPhe · F	UCCSer · S	UACTyr · Y	UGCCys · C	C
	UUALeu · L	UCASer · S	UAAStop	UGAStop	A
	UUGLeu · L	UCGSer · S	UAGStop	UGGTrp · W	G
C	CUULeu · L	CCUPro · P	CAUHis · H	CGUArg · R	U
	CUCLeu · L	CCCPro · P	CACHis · H	CGCArg · R	C
	CUALeu · L	CCAPro · P	CAAGln · Q	CGAArg · R	A
	CUGLeu · L	CCGPro · P	CAGGln · Q	CGGArg · R	G
A	AUUIle · I	ACUThr · T	AAUAsn · N	AGUSer · S	U
	AUCIle · I	ACCThr · T	AACAsn · N	AGCSer · S	C
	AUAIle · I	ACAThr · T	AAALys · K	AGAArg · R	A
	AUGMet · M (start)	ACGThr · T	AAGLys · K	AGGArg · R	G
G	GUUVal · V	GCUAla · A	GAUAsp · D	GGUGly · G	U
	GUCVal · V	GCCAla · A	GACAsp · D	GGCGly · G	C
	GUAVal · V	GCAAla · A	GAAGlu · E	GGAGly · G	A
	GUGVal · V	GCGAla · A	GAGGlu · E	GGGGly · G	G

Codon lookup

Type 3 bases (A, C, G, and U or T).

The standard genetic code

The codon table maps each of the 64 three-base codons to the amino acid it specifies during translation, or to a stop signal that ends the protein. This chart is the standard genetic code (NCBI translation table 1), the one shared by almost all life and taught in every molecular biology course. Read it in the classic 4×4×4 layout: the first base picks the row block down the left edge, the second base picks the column across the top, and the third base picks the row inside each block down the right edge. Cells are tinted by the amino acid's side-chain class — the same colours used on the Amino Acids chart — so patterns like the four-fold degenerate boxes jump out at a glance.

Start and stop codons

AUG codes for methionine and doubles as the start codon that sets the reading frame for translation — it is outlined on the chart. Three codons encode no amino acid and instead stop translation: UAA (ochre), UAG (amber), and UGA (opal), shaded grey here. The code is redundant: most amino acids are specified by more than one codon, which is why swapping the DNA↔RNA toggle changes only how the bases are written (U for uracil in RNA, T for thymine in DNA) and never which residue a codon encodes. Use the codon lookup to type any three bases — in DNA or RNA, upper or lower case — and see the residue.

How the quiz works

Each round shows one random codon and four possible answers — amino acid names or Stop. Pick the one you think the codon encodes; the quiz marks it right or wrong, reveals the correct residue, and keeps a running score, current streak, and best streak for the session. Press Next codon for a new card or Reset score to start over. Every codon and answer choice is drawn with secure browser randomness, entirely in your browser. For related tools, generate a Random DNA Sequence or Random Protein Sequence, or study the Amino Acids chart.

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