In blue-white selection what does a white colony generally indicate?

Correct answer: A potential recombinant clone in which foreign DNA insertion has disrupted lacZ

In blue-white selection, insertion of foreign DNA within lacZ can disrupt lacZ function. As a result, β-galactosidase is not produced and X-gal is not converted into a blue product, so the colony appears white. In contrast, an active lacZ gene generally produces a blue colony. Exam tip: treat a white colony as a potential recombinant and remember that further screening or analysis may be needed for confirmation.