Figure 1.

Balance of codons in the classic circular genetic code. Rectangles are surrounding the odd-numbered codons present in quadrants one and three and the paired groups of codons that are present in quadrants two and four ([a]-[d], quadrants 1-4, respectively). Only quadrants two and four are fully symmetrical, both by number and by position. Here, the rectangles specifically represent the quasi-symmetrical position of the odd-numbered groups of codons for quadrants one and three, and of paired groups of codons for quadrants two and four, having equilibrium in the net sum for these codons per quadrant (numbers in bold). A similar numerical balance is seen in the essential hydrophobic amino acids with U at the center of their codons (ref. ⁴).