Codon Chart

A FIELD GUIDE TO THE GENETIC CODE

Follow the codon wheel.

Read from the center outward: first base, second base, third base, then amino acid.

Read 5′ to 3′ · first, second, third base
Standard Code codon wheelGenetic code 1; NCBI genetic-code tables, September 23, 2024. Read 5′ to 3′, center outward. Generated by Codon Chart.UCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGUCAGPhePheLeuLeuSerSerSerSerTyrTyrStopStopCysCysStopTrpLeuLeuLeuLeuProProProProHisHisGlnGlnArgArgArgArgIleIleIleMetThrThrThrThrAsnAsnLysLysSerSerArgArgValValValValAlaAlaAlaAlaAspAspGluGluGlyGlyGlyGly5′ → 3′START HERE
NonpolarPolarAcidicBasicStop

Standard code (NCBI table 1). Start-codon use depends on the organism and sequence context.

Reading from the center outward

Start with the first base of your codon in the innermost letter ring. Move outward through the second and third bases, then read the amino acid at the edge. For UGG, follow U, then G, then G to reach tryptophan, abbreviated Trp or W. Always read the input codon 5′ to 3′; the wheel is not a template-strand decoder.

The wheel and codon table show the same assignments in different arrangements. Select a segment at the outside of the wheel to inspect that codon, or use the three labeled base selectors. These selectors also provide a keyboard-accessible way to look up any assignment without clicking a narrow segment.

RNA, DNA and alternative codes

Most classroom wheels use RNA letters. Switching to DNA replaces U with T; it does not reverse or complement the sequence. If you have the DNA template strand, first establish its direction and obtain the coding-strand sequence with the reverse complement tool.

The standard genetic code is the default. The code selector also contains the mitochondrial and other alternative tables published by NCBI. Some assignments depend on context. A dagger marks an amino-acid assignment that can also act as termination; the note below the wheel identifies those codons. A wheel alone cannot establish the biological context that resolves such an assignment.

A wheel for printing

The SVG download is a vector illustration with text labels, so you can scale it for a handout or slide. Print removes the navigation and lookup controls. For longer sequences, the DNA-to-protein translator calculates reading frames directly and reports incomplete codons and unresolved assignments. The amino acid reference provides full names alongside one-letter and three-letter abbreviations.