While there is much commonality, different parts of the tree of life use slightly different genetic codes. When translating from genome to protein, the use of the correct genetic code is essential. The mitochondrial codes are the relatively well-known examples of variation. The translation table list below follows the numbering and designation by NCBI.
Four novel alternative genetic codes were discovered in bacterial genomes by Shulgina and Eddy using their codon assignment software Codetta, and validated by analysis of tRNA anticodons and identity elements; these codes are not currently adopted at NCBI, but are numbered here 34-37, and specified in the table below.
Data format
Most data in this page is derived from the NCBI Genetic codes database, which consists of a machine-readable gc.prt file succinctly describing each translation table and some additional notes only visible on an associated web page wprintgc.cgi.
For each translation table, the gc.prt file provides its name(s), numeric id, and two 64-character tables called ncbieaa and sncbieaa. These tables map to the codons in the order of TTT, TTC, TTA, TTG, TCT, ... GGG; each character corresponds to the one-letter IUPAC amino acid code with the addition of * (termination) and - (gap). The former table is used for regular translation. The latter table is used to indicate initiation (if it contains a letter: at present only M for methionine), termination (if it contains a *), or neither (-). For usual ("unconditional") stop codons, a * is present in the equivalent positions of both tables. For conditional stop codons where a codon can either be stop or sense (tables 27, 28, 31), the ncbieaa table contains the sense translation, while sncbieaa has * indicating the possibility of a stop.
gc.prt also includes some non-machine-readable change history in comment form. The associated web page wprintgc.cgi provides notes and references for human reading.
As can be seen from the notes, the simple table format necessarily includes some flattening of biological variations for tables that cover broad taxonomic ranges. An example is the standard code (1), which originally only provided for AUG initiation, but was later changed to add UUG and CUG. However, this description still excludes known cases of GUG initiation known among fungi and mammals.
Table summary
This section is missing information about start codon in these tables, aka the "sncbieaa" row in NCBI data. Please expand the section to include this information. Further details may exist on the talk page.(December 2023)
Comparison of alternative translation tables for all codons (using IUPAC amino acid codes):
Pyrrolysine (Pyl or O), which requires no special machinery to insert so long as Pyl-tRNAPyl is available. As a result, it can and has appeared in proteins through neutralmissense mutations. Indeed, Pyl is so widespread among some lineages of archaea that their genetic code can be said to be a new "Pyl code".
