sentences:  The names stem from the conserved nucleophilic amino acid residue present in each class of recombinase which is used to attack the DNA and which becomes covalently linked to it during strand exchange.The earliest identified members of the serine recombinase family were known as resolvases or DNA invertases, while the founding member of the tyrosine recombinases, lambda phage integrase (using attP/B recognition sites), differs from the now well-known enzymes such as Cre (from the P1 phage) and FLP (from the yeast "Saccharomyces cerevisiae").Famous serine recombinases include enzymes such as gamma-delta resolvase (from the Tn"1000" transposon), Tn3 resolvase (from the Tn3 transposon), and "φ"C31 integrase (from the "φ"C31 phage).