hadasali

Hi, I did electroporation to insert to BL21 DE3 cells with pACDK4C plasmid which contains Cap resistance gene and Targetron (intron that can integrate into a specific location) that inserts to LacZ gene. The Taregetron cannot be transcribe without IPTG presence due to the fact that it located downstream to T7 promoter and Lac operator. I plated the transformants on LB+Cap (25ug/ml) plate. As negative control I plated BL21 cells without the plasmid on LB plate. Both plates were applied with 60ul Xgal (20ug/ml) + 40ul IPTG 0.1M. The strange thing was that in the LB+Cap plates the cells only grow in the edges of the plate while in the negative control the colonies grow on top of the entire plate. Also all colonies both in the experiment plates and in the Negative control plates were blue. Does anybody have an explanation to that? Thanks =)