In recombinant DNA tech, To select a recombinant host from non-recombinants, we have different types of techniques available.
The one I'm talking about is the color selection method with the use of 2 markers(one antibiotic resistant gene for eg. Ampicillin, and the other Z-gene). We use Z-gene as the reporter gene. We use vectorless E. Coli as the host cell here.
Now, when we add add Ampicillin to the petri dish containing all of the variants (transformants and non-transformants), - the non-transformants will die. The transformants survive.
Now, we add X- gal to the replica of this petri dish, and we see some of the colonies turning blue due to the action of the enzyme β- galactosidase, which in turn is produced by the intact Z-gene in the plasmid. That means our blue colonies are the non-recombinant ones.
My question is-
The medium taken in the petri dish should contain glucose too , shouldn't it? Otherwise the recombinants would too give the colour reaction (X-gal is a homolog of lactose) due to the Z-gene present in their chromosomal DNA (operon concept).
The question maybe silly since it's kind of obvious we have to supply basic necessities for the growth of bacteria(which obioviously is glucose).
Just wanted to confirm in case we don't have glucose available ! =p