The scheme of the Metabolically Coupled Replicator System without and with template-directed replication. Panel A: The original metabolic replicator system based on . Four autocatalytic metabolic replicators (I
, i = 1, .., 4 within the circular arrows). M is the metabolic reaction network supported by the metabolic replicators as enzymes (solid lines) and producing monomers for their replication (dashed lines). Panel B: the same as Panel A but the system contains a parasitic (P) replicator besides metabolic (I
, where i = 1..3) ones. Parasites consume monomers produced by the metabolic network but do not contribute to the production of monomers. Panel C: the Metabolically Coupled Replicator System in which all reactions of a hypothetical metabolic-network (M) are catalysed (solid arrows) by the phenotype forms of replicators (Ph
, where x = 1, …, 4). Dashed arrows show that replicators consume the end-products of the metabolic-network (monomers). Dotted, double-headed arrows depict template-dependent replication process which produces phenotype from genotype (G
) during a replication event, and vice versa. Panel D: shows parasites in the same system like in Panel C. P
are the two forms of the parasite.