IUPAC Codes
Nucleotides
| Code | Bases | Meaning |
| A | A | Adenine |
| C | C | Cytosine |
| G | G | Guanine |
| T | T | Thymine |
| U | U | Uracil |
| R | A or G | Purine |
| Y | C or T | Pyrimidine |
| S | G or C | Strong |
| W | A or T | Weak |
| K | G or T | Keto |
| M | A or C | Amino |
| B | C, G or T | Not A |
| D | A, G or T | Not C |
| H | A, C or T | Not G |
| V | A, C or G | Not T |
| N | A, C, G or T | Any base |
| - | Gap |
Amino acids
| Code | Three-letter | Name |
| A | Ala | Alanine |
| R | Arg | Arginine |
| N | Asn | Asparagine |
| D | Asp | Aspartic acid |
| C | Cys | Cysteine |
| Q | Gln | Glutamine |
| E | Glu | Glutamic acid |
| G | Gly | Glycine |
| H | His | Histidine |
| I | Ile | Isoleucine |
| L | Leu | Leucine |
| K | Lys | Lysine |
| M | Met | Methionine |
| F | Phe | Phenylalanine |
| P | Pro | Proline |
| S | Ser | Serine |
| T | Thr | Threonine |
| W | Trp | Tryptophan |
| Y | Tyr | Tyrosine |
| V | Val | Valine |
| U | Sec | Selenocysteine |
| O | Pyl | Pyrrolysine |
| B | Asx | Asparagine or aspartic acid |
| Z | Glx | Glutamine or glutamic acid |
| J | Xle | Leucine or isoleucine |
| X | Xaa | Any amino acid |
| * | Ter | Stop |
How to use IUPAC Codes
- The first table lists the nucleotide codes and the bases each one stands for.
- The second lists the amino acid codes with their three-letter codes and names.
Frequently asked questions
What does N mean in a DNA sequence?
Any base: A, C, G or T. It is used where the base is unknown.
What are B, Z and J in a protein?
B is asparagine or aspartic acid, Z is glutamine or glutamic acid, and J is leucine or isoleucine, for when the two cannot be told apart.
More DNA and protein sequence tools
Reverse ComplementDNA to RNACombine FASTA SequencesSplit FASTA SequenceGenBank to FASTAEMBL to FASTAGenBank Feature ExtractorEMBL Feature ExtractorGenBank Translation ExtractorEMBL Translation ExtractorSplit CodonsRange Extractor DNARange Extractor ProteinWindow Extractor DNAWindow Extractor ProteinFilter DNAFilter ProteinGroup DNAGroup ProteinOne-Letter to Three-Letter Amino AcidsThree-Letter to One-Letter Amino AcidsDNA StatisticsProtein StatisticsCodon UsageCpG Island FinderDNA Molecular WeightProtein Molecular WeightProtein Isoelectric PointProtein GRAVYDNA Pattern FindProtein Pattern FindFuzzy Search DNAFuzzy Search ProteinIdentity and SimilarityORF FinderTranslate DNA to ProteinReverse TranslateReverse Translate a Protein AlignmentPCR Primer StatsPCR ProductsRestriction SummaryMutate for DigestPairwise Align DNAPairwise Align ProteinPairwise Align CodonsRestriction MapTranslation MapPrimer MapColor Alignment by ConservationColor Alignment by PropertiesCodon PlotRandom DNA SequenceRandom Protein SequenceRandom Coding DNARandom DNA RegionsRandom Protein RegionsSample DNASample ProteinShuffle DNAShuffle ProteinMutate DNAMutate ProteinGenetic Codes