The score for the 'Zip' portion of the model is obtained from the number of consecutive matching trimers, tetramers etc, up to pentadecamers, each counted with equal weight, within a contiguous matching segment. Thus, ZipScore modex = AE k = 1 k = kmax (AE n = 3 n = 15 S n ), where kmax is the number of uninterrupted matching segments, including the chosen nucleation site, and S n is the number of successive segments of length n (varying from 3-15), i.e. the number of full length trimers, full length tetramers etc. up to full length pentadecamers, which fit into the matching segment. The same Zip scoring system was performed in two modes, counting dInosines either as matching (mode 1) or as mismatching (mode 2). In the second mode, dInosines will shorten the length of matching segments, decreasing the score. The final ZipScore was calculated as a weighted mean of ZipScore mode1 and ZipScore mode2 , where the weighting factor was based on the empirical data presented in the current report (Figures 2-4) . Since dInosine hybridizes more strongly to C than to the other nts, the algorithm adds a contribution based on the number of dI:C pairs weighted by an InoCfactor. The upstream and downstream ZipScores were obtained as: ZipScore downstream =ZipScore mode1 -dInosinefactor (ZipScore mode1 -ZipScore mode2 )+(dInoCnr * dInoCfactor) and ZipScore upstream = ZipScore mode1 -dInosinefactor (ZipScore mode1 -ZipScore mode2 )+(dInoCnr * dInoCfactor).