Table 1.
Properties of the two recombination mechanisms in the in vitro Qβ system
| Self-recombination | Replicase-assisted recombination | |
| Reaction kinetics | Pseudo-first order | Second order |
| Rate-limiting step | Chemical reaction | Non-covalent interactions |
| Overall ratea, nt−1 h−1 | 10−9 | 10−4–10−5 |
| Nucleophilic attack | By 2′-OH | By 3′-OH |
| Reacting nt | Internal | 3′-Terminal+internal |
a
The rates have been extrapolated to the intracellular phage RNA concentration. Their values can be directly compared with the recombination frequency in RNA phages whose infection cycle takes about 1 h.