Genetic code theoretically possible

The behavior and properties of P. are determined by their structures Theoretically, there is no limit to polypeptide chain length, and all permutations and combinations of the 20 constituent amino acids are possible (see Genetic code). Further possibilities for structural variation are offered by Post-translational modification of proteins (see), attachment of nonprotein prosthetic groups, and different levels of quaternary structure, so that the possible diversity of structure (and therefore function) is almost limitless. 

FIGURE 12.2 Theoretically possible genetic codes, (a) An overlapping versus a nonoverlapping code, (b) A continuous versus a punctuated code. 

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