Question

To screen for cells that have picked up a plasmid with a cloned DNA fragment following transfection, lacZ- cells are grown on agar medium containing X-gal, the antibiotic ampicillin, and IPTG.

a. True
b. False

Answer 1

Cells with a cloned DNA fragment containing a foreign insert are screened by growing them on agar medium containing X-gal, ampicillin, and IPTG. Plasmids lacking the insert turn the colony blue, while plasmids with the insert produce white colonies.

Step-by-step explanation:

To screen for cells that have picked up a plasmid with a cloned DNA fragment following transfection, lacZ- cells are grown on agar medium containing X-gal, the antibiotic ampicillin, and IPTG. The ampicillin kills bacteria without plasmid. Plasmids lacking the foreign insert have an intact lacZ gene and are able to metabolize X-gal, releasing a dye that turns the colony blue. Plasmids with an insert have a disrupted lacZ gene and produce white colonies.