Abstract: Disclosed are replicatable viral DNA vectors encoding a site-specific DNA-altering enzyme and a DNA target recognized by the enzyme, the enzyme selectively converting, in a cell expressing the enzyme, the DNA vector to a rearranged form. The invention further relates to methods for assembling recombinant adenoviral DNAs. These methods include the steps of: (a) providing a first linearized DNA vector including a restriction site and a cos site and a second linearized DNA vector including the restriction site, an adenoviral nucleic acid molecule, and a cos site; and (b) ligating the first and second linearized DNA vectors, the ligation assembling a recombinant adenoviral DNA.