Suppose that a particular amino acid has a given degeneracy, for example 2. This means that two different redundant codons code for the same amino acid, but which codons? It is clear that the degeneracy does not change if we change the two specific codons assigned to this amino acid choosing them from the other 62 existing ones: once we pick out specific codons for all the degeneracies we have specified a particular codon assignation for the specific degeneracy distribution of Table 2. This codon assignation represents a second level of complexity: once a degeneracy distribution is assigned we must fill out the code with specific codons, that is, we must specify the codon assignation in the degenerate code. In Table 3 such a codon assignation for the case of the standard genetic code is given as a translation table with three different entries corresponding to four different letters (U, C, A, G).
In Table 4 we give also the euplotid nuclear version of the genetic code. This version differs from the standard genetic code only in the assignation of the variable codon UGA, which in the latter case is assigned to Cysteine instead of to the stop signal.
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