Final answer:
The LB agar with ampicillin and a plasmid containing the lac operon will allow growth of ampicillin-resistant bacteria. These bacteria will form blue colonies if they have an intact lacZ gene, which metabolizes X-gal, or white colonies if the lacZ gene is disrupted by the insertion of foreign DNA.
Step-by-step explanation:
The result of an LB agar with ampicillin given a plasmid with the lac operon and lactose will exhibit a selection of bacteria that have taken up the plasmid. When bacteria are grown on media that contains ampicillin and X-gal, a substance similar to lactose, only bacteria with the plasmid conferring ampicillin resistance can survive. This is because ampicillin kills bacteria that are sensitive, i.e., those without the plasmid. If the plasmid contains an intact lacZ gene, the bacteria can metabolize X-gal and release a dye that turns the colony blue. However, if there is a foreign DNA insert within the lacZ gene, the gene will be disrupted, and the bacteria will not metabolize X-gal, resulting in white colonies. Thus, blue colonies indicate plasmid with an intact lacZ gene, and white colonies indicate recombinant plasmids with disrupted lacZ due to the insertion of foreign DNA.