DNA Codon Table and Amino Acid Chart

All 64 codons

Codons for each amino acid

Most amino acids have more than one codon. These synonymous codons usually differ only in the third base, so some single-letter changes in DNA leave the protein unchanged.

Start and stop codons

Translation usually begins at ATG (AUG in RNA), which also encodes methionine. Because ATG also appears inside genes, not every ATG is a start codon: cells use nearby signals in the messenger RNA to choose where to begin.

Three codons — TAA, TAG, and TGA (UAA, UAG, and UGA in RNA) — are stop codons. They do not encode an amino acid; they tell the ribosome that the protein is finished.

The Standard Genetic Code is used by most organisms, but not all. Mitochondria and some microbes use slightly different codes — in human mitochondria, for example, TGA encodes tryptophan instead of stop. NCBI lists these variants as separate translation tables.

DNA codons and RNA codons

DNA and RNA use the same code with one letter changed: DNA contains thymine (T), and RNA contains uracil (U) in its place. When a gene is transcribed, the messenger RNA has the same sequence as the gene's coding strand, except that every T becomes U. That is why GCT in a DNA codon table and GCU in an RNA codon table both mean alanine.

DNA

ATG GCT AAA TAA

RNA

AUG GCU AAA UAA

Protein

Met Ala Lys Stop

The chart above lists both spellings, so it works with either kind of sequence.

DNA My Name's letter substitutions

These are site rules, not part of the genetic code. The 20 standard amino acids use 20 of the 26 letters of the alphabet. So that every name can be spelled, DNA My Name swaps each of the other six letters for a standard amino acid. This is a creative choice made by this site. In biochemistry some of these letters have their own meanings — U is selenocysteine, O is pyrrolysine, and B, J, X, and Z mark ambiguous or unknown amino acids — but none of them has its own codon in the Standard Genetic Code.

Every other character follows a separate site rule. Spaces, digits, punctuation, accented letters such as é, emoji, and letters from other alphabets each become the placeholder codon AAA, which the Standard Genetic Code reads as lysine, so they appear as K in a name's amino acid sequence. This placeholder is not part of the genetic code.

Codon table FAQ

Use the codon table

Download the codon chart

A printable DNA codon table for handouts, slides, and classroom walls. It arranges all 64 DNA codons by first, second, and third base and labels each with its amino acid's three-letter abbreviation or Stop. A key gives the full amino acid names, ATG is marked as the common start codon, and a note explains that RNA uses U in place of T.

Free to download for personal and classroom educational use. Please keep the attribution on the chart visible. To republish it, use it commercially, or embed it on another website, email feedback@dnamyname.com.