The genetic code assembles via division and fusion, basic cellular events

Abstract

AbstractStandard Genetic Code (SGC) evolution is quantitatively modeled in computed ‘worlds’ containing up to 2000 independent coding ‘environments’. Environments can host multiple codes that may fuse or divide, with division yielding identical descendants. Code division may be selected - sophisticated gene products could be required for orderly separation. Several unforeseen results emerge: more rapid evolution requires unselective code division, rather than its selective form. Combining selective and unselective code division, with/without code fusion, with/without independent environmental coding tables and with/without wobble defines 25= 32 possible pathways for SGC evolution. These 32 possible histories are compared, particularly, for speed and accuracy. Pathways differ greatly; for example, ≈ 300-fold different in time to evolve SGC-like codes. Eight of 32 pathways, employing code division, are quickest. Four of these eight, that combine fusion and division, also unite speed and accuracy. The two precise, swiftest paths, thus the most likely routes to the SGC, are similar, differing only in fusion with independent environmental codes. Code division instead of fusion with unrelated codes implies that independent codes can be dispensable. Instead, a single ancestral code that divides and fuses can initiate fully encoded peptide biosynthesis. Division and fusion create a ‘crescendo of competent coding’, facilitating search for the SGC, and also assist advent of otherwise disfavored wobble coding. Code fusion readily unites multiple codon assignment mechanisms. But via code division and fusion, the SGC is shown to emerge from a single primary origin, via familiar cellular events.