The plasmid vector I am referring to is pCR 2.1 - TOPO. I added the vector to the E coli and plated them up onto LB+amp+X-gal plate, then incubated. After incubation the plates had two types of bacterial culture on them, one white and one blue.
I think that the blue cultures have accepted the plasmid as they are able to grow on ampicillin, so have the ampicillin resistance gene, and are able to convert the X-gal substrate to blue via the lac Z gene. What i'm confused about is the white colonies. If the colonies are able to grow on ampicillin, surely they have accepted the gene because they have the resistance, and surely they should to be able to convert the X-gal?
So why are these not expressing the lac Z gene? Is it that the lac Z gene and ampicillin resistance aren't on the same plasmid, or is it that the lac z gene didn't make it into the plasmid?