The fundamental nature of the genetic code: prebiotic interactions between polynucleotides and polyamino acids or their derivatives.

Abstract

The hypothesis is given that evolution of the cell began with 2 general kinds of polymers, polynucleotides that were purine-rich and polyamino acids composed largely if not solely of basic amino acids. One type of polymer is viewed as catalyzing, in particular ways, the synthesis of the other, and vice versa. The plausibility of the present scheme rests in large part upon the availability in a primitive environment of appreciable quantities of basic amino acids. Although lysine has been reported to be synthesized under "primitive earth conditions", the yield is low. However, in dealing with primitive polyamino acids one is not restricted to those basic amino acids now found "encoded" in cells-i.e., lysine, arginine, and histidine. 2,4 diaminobutyric might well have been relatively abundant on the primitive earth, for it is probably synthesized from compounds which may have been very abundant and/or reactive[long dash]i.e., [beta] -amino propionitrile or derivatives of aspartic acid. The dominant relationship between polynucleotides and polyamino acids was initially a colinear 1:1 physical binding, probably not unlike that occurring in DNA:histone complexes today (which raises the possibility that one function of modern histones might be in accumulation of nucleic acid monomer units). This polynucleotide:polyamino acid relationship is simpler than most of its modern counterparts. Consider nucleic acid tape reading, or enzymatic production of activated mono-nucleotides, etc. According to the present model, translation began as a "direct templating" and in addition, "translation" was initially a reciprocal matter, not unidirectional as it is now. The coding ratio for primitive translation was unity, compared to the contemporary value of three. Probably the most important difference between "translation" now and then was the extreme inaccuracy, the ambiguity of the primitive version. There is doubt that such an imprecise ordering could be termed "translation".