FIGURE 5.2 - Spreading test plates. (a) 50 µl of transformation culture is placed in the center of an X/I/C plate. A sterile plating rod is used to distribute the transformation reaction evenly across the surface of the plate. (b) Test plates are incubated for 15-24 hours at 37°C. Bacteria without a plasmid lack the resistance gene to chloramphenicol (CM) and thus cannot grow on the X/I/C agar. Blue colonies contain a plasmid, however they are producing ß-galactosidase (evident by their ability to convert X-GAL into a blue precipitate) indicating that they do not contain inserts. White colonies represent bacteria that contain a plasmid with an insert (hopefully a large piece of genomic DNA) at the multiple cloning site in the ß-galactosidase gene (thus disrupting the gene's activity).