Blue/White selection , Preparation of Plasmid DNA

* Spread the following on a LB (+appropriate antibiotic) plate (If you are going to plate 100ul of transformed cells): 100ul of 100mM IPTG + 40ul of X-gal (20mg/ml).
* Perform transformation of ligation into the bacteria (note: make sure you are using the right host bacterial strain for the blue white selection, also see the background section below) and then spread them on the X-gal containing plates.
* After overnight incubation, store the plate in 4 0 C for several hours. This allows the blue color to develop fully. Colonies that contain active b -galactosidase are pale blue in center and dense blue at their periphery. White colonies occassionally show a faint blue spot in the center, but these are colorless at the periphery.
Stock solutions:
* X-gal-X-gal is very expensive, and hence avoid wastage. X-gal stock solution can be prepared by dissolving 100mg of X-gal in 5ml of dimethyl formamide. X-gal is light sensitive and hence store in a glass or polypropylene containers wrapped with aluminium foil. Stock sloution need to be store in -20 0 C