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The National Center for Biological Information (NCBI) syntax for a translation table is a string of sixty-four amino acids and stop characters. Each position in the string corresponds to a codon, a three-letter sequence of the four DNA bases. All such codon translations are defined by these sixty-four characters (43=64). The sequence TCAG is used to enumerate these positions so that TTT is at the first position, TTC is at the second position and so forth.
For example, consider "FFLLSSSSYY**CC*WLLLLPPPPHHQQRRRRIIIMTTTTNNKKSSRRVVVVAAAADDEEGGGG". By aligning this specification with an enumeration of the series, we can read down from the first position to see that "F" is in the first and second positions and thus is the translation of "TTT" and "TTC", while "I" lines up with "ATT", "ATC" and "ATA":
TTTTTTTTTTTTTTTTCCCCCCCCCCCCCCCCAAAAAAAAAAAAAAAAGGGGGGGGGGGGGGGG (1st letter)
TTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGG (2nd letter)
TCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAG (3rd letter)
In the NCBI syntax, the character "*" represents a stop character. When following IUPAC convention, a period is used as a stop character.