Figure 1.
Non-templated polymerization and template-directed synthesis occur inside a model system using activated monomers supplied from the exterior. Replication begins when a primer (of length k) binds to a template (of length n) so that their ends are aligned. Template-directed elongation occurs until the primer has been extended to a sequence of length n. The pair then dissociates, yielding the original template and a copy. The two sequences can then begin a new cycle of replication. Activated monomers can be hydrolyzed, thereby losing activation, and all sequences are degraded at a fixed rate.