sentences:  Although the individual members of the two recombinase families can perform reactions with the same practical outcomes, the families are unrelated to each other, having different protein structures and reaction mechanisms.Unlike tyrosine recombinases, serine recombinases are highly modular, as was first hinted by biochemical studies and later shown by crystallographic structures.Knowledge of these protein structures could prove useful when attempting to re-engineer recombinase proteins as tools for genetic manipulation.