homologous recombination - (Dec/11/2006 )

hi every body,
i am a new member in this bioforum.
can some one help me to detect where the problem is.
i am trying to make homologous recombination between a circular plasmid and ds DNA virus in mammalian cells. i used lipofectamine ransfection.
i have good expression of the plasmid and CPE appear after 2-3 days but no recombination occur ?

i have no exp in it but you may have a look at Vogelstein work in NAR