Fig. 5

Key events associated with the relation, difference and interaction between RNA and DNA. The diagram shows one grid room in the model which is occupied by a protocell. Legends: Npp, nucleotide precursor’s precursor; Np, nucleotide precursor; Nt, nucleotide; Ap, amphiphile precursor; Am, amphiphile; Dnpp, deoxynucleotide precursor’s precursor; Dnp, deoxynucleotide precursor; Dnt, deoxynucleotide; the notations of ribozymes are the same as in the text. The parameters shown in bold type are those newly introduced which are explained in Table 1, and the others are “old ones” whose descriptions can be found in Table 2. Note that while the rate of chain breaking (hydrolysis) for RNA is represented by P _BBR , that for DNA is defined as P _BBR  × F _BBD – wherein, F _BBD  < <1. The tendency of a nucleic acid chain turning to template is inversely proportional to the factor for its folding, which is F _SFR for RNA and F _SFD for DNA – wherein, F _SFR  > F _SFD (and so DNA is easier to act as a template than RNA). The fidelity of the template-directed copying is associated with the probability of false base-pairing tolerated at each residue site when the substrates (monomers or oligomers) are attracted onto the template, which are here represented respectively by P _FPRR , P _FPRD , P _FPDD , and P _FPDR according to the type of the template as well as the type of the substrates. The replication of DNA is more accurate than that of RNA replication – i.e., P _FPDD  < P _FPRR . See the text for details