Table 1.

Class distribution over all possible base-pairs between the 64 codons of the genetic code, weighted with the natural codon frequency of both codons (left). Class distribution based on the RNA secondary structure as depicted in Figure 2 (right)

	Codon frequency based			mRNA structure based
	c1	c2	c3	c1	c2	c3
Archaea	31.7	33.8	34.4	25.2	37.8	37.3
Bacteria	32.1	33.7	34.1	27.0	36.3	36.7
Fungi	32.5	33.7	33.7	30.1	35.2	34.1
Invertebrates	32.8	33.5	33.5	30.3	33.5	36.0
Plants	32.8	33.5	33.5	31.2	33.9	34.9
Protozoa	32.7	33.5	33.6	29.6	34.0	36.1
Mammals	32.7	33.6	33.5	29.8	35.1	35.0
Vertebrates	32.8	33.6	33.5	30.3	34.6	35.0
Viruses	32.4	33.8	33.6	30.2	34.8	34.8