Bacteria that contain the vector plasmid pBluescript II produce blue colonies if grown in a special medium. If these bacteria contain recombinant DNA, inserted into the LacZ gene of the plasmid, they produce white colonies. This is useful because it
A) provides a way of mapping DNA segments.
B) identifies the plasmid from the bacterial DNA.
C) separates different genome fragments.
D) provides a way of identifying transformed bacteria.
E) identifies transposons integrated into the bacterial genome.

Question

Quizplus · Accepted Answer

This is an example of blue-white screening, a technique used to identify bacterial colonies that have been successfully transformed with a plasmid containing an insert of interest. The presence of white colonies indicates that the LacZ gene in the plasmid has been disrupted by the insertion of foreign DNA, thereby preventing the production of the enzyme β-galactosidase which is required to metabolize the substrate in the medium into a blue product. Thus, white colonies indicate successful transformation with recombinant DNA.

Bacteria That Contain the Vector Plasmid PBluescript II Produce Blue