When trying to do RMCE (recombinase-mediated cassette exchange), I add the new DNA sequence with LoxP and Lox2272 sites along with Cre recombinase, so then it switches out genes from my original construct in the cell (also containing LoxP and Lox2272).

Does the new DNA sequence have to be in a circularized vector? or can it just be a linear dsDNA strand? In the diagrams I always see the newly introduced DNA as part of a vector, but I assume this is because typically we amplify the DNA in vectors using e.coli etc, not because it's strictly necessary for RMCE.

e.g Article Site-directed integration of the cre gene mediated by Cre re...