Table 1. Comparison of the properties of site-specific, transpositional, and IS30 IR–IR-mediated recombination.

Characteristics	Site-specific recombination	(IR–IR) × (IR–IR)	Transposition
Mechanism	Conservative	Conservative	Conservative or replicative
Frequency of recombination	High	High	Low
Specific sequence requirements on
Donor DNA	Yes (res, dix, att, lox, dif)	Yes (IR–IR)	Yes (IR)
Target DNA	Yes (res, dix, att, lox, dif)	Yes (IR–IR)	Variable specificity
Target site after recombination	Unaltered	Unaltered	Duplicated or unaltered
Host factors	None or IHF, HU, FIS, etc.	None	None or IHF, HU, FIS, etc.
Catalytic motif involved*	Active Ser/Tyr, DED/DDD,	DDE	DDE, active Tyr, DED/DDD

^*Active Ser, Invertase/resolvase family; active Tyr, integrase family; DED/DDD, Piv/Moov/IS110 family; DDE, transposase/retroviral integrase family