The editor for sequence data recognizes predefined symbols for nucleotide and protein sequences according the IUPAC definitions.
| Symbol | Name |
| A | Adenine |
| C | Cytosine |
| G | Guanine |
| T | Thymine |
| U | Uracile |
| W | Weak (A or T) |
| S | Strong (G or C) |
| M | aMino (A or C) |
| K | Keto (G or T) |
| R | puRine (G or A) |
| Y | pYrimidine (C or T) |
| B | not A (B comes after A) |
| D | not C (D comes after C) |
| H | not G (H comes after G) |
| V | not T (V comes after T and U) |
| N | No idea (not a gap) |
The symbols with grey background are ambiguity symbols. The difference between "N" and a gap symbol (usually "-", but any other symbol may be defined in the descriptor) is that a gap symbol represents an unspecified number of unknown symbols but "N" stands for exatly one nucleic acid.
| Name | 1-letter sybmol | 3-letter sybmol |
| Alanine | A | Ala |
| Arginine | R | Arg |
| Asparagine | N | Asn |
| Aspartic acid | S | Asp |
| Cysteine | C | Cys |
| Glutamic acid | E | Glu |
| Glutamine | Q | Gln |
| Glycine | G | Gly |
| Histidine | H | His |
| Isoleucine | I | Ile |
| Leucine | L | Leu |
| Lysine | K | Lys |
| Methionine | M | Met |
| Phenylalanine | F | Phe |
| Proline | P | Pro |
| Serine | S | Ser |
| Threonine | T | Thr |
| Tryptophan | W | Trp |
| Tyrosine | Y | Tyr |
| Valine | V | Val |
| Selenocysteine | U | Sec |
| Pyrrolysine | O | Pyl |
| Asparagine or aspartic acid | B | Asx |
| Glutamine or glutamic acid | Z | Glx |
| Leucine or Isoleucine | J | Xle |
| Unspecified or unknown amino acid | X | Xaa |
The symbols with grey background are ambiguity symbols. The difference between "X" rsp. "Xaa" and a gap symbol (e.g. "---", but any other symbol may be defined in the descriptor) is that a gap symbol represents an unspecified number of unknown symbols but "X" rsp. "Xaa" stand for exatly one amino acid. The amino acids "Selenocysteine" and Pyrrolysine" are non-standard amino acids that only occur in certain species.
Continue with: