Will all the pups born following microinjection carry the transgene?
No, integration of the microinjected transgenic DNA into the embryonic genome is not very efficient. Therefore, only about 10-30% of pups will have inherited the transgene. Since integration most often occurs prior to the first zygotic cell division, the transgene will be present in all nucleated cells of those mice, the founder (F0) mice, that inherit the transgene. While all of the founder mice carry the exact same transgene, integration of the transgene is a random event. Therefore, each founder is considered unique with respect to the chromosomal location or integration site of the transgene, the number of transgene copies integrated at that site, and the expression pattern of the transgene.
