Computation of the fraction of RNA sequences that fold sequentially into a unique free-energy minimum

We compute the fraction of RNA sequences of fixed length N=220 that fold expeditiously and reproducibly into a unique structure within realistic RNA replication time spans. The search in conformation space is assumed to be concurrent with the assembling of the molecule which occurs by sequential incorporation of nucleotides. Monte Carlo simulations of the folding events concomitant with polymerization events are used to determine the evolutionary consequences of the principle of expeditious and reproducible folding hereby introduced.