Final answer:
Blue colonies during a genetic engineering project signify bacterial cells with empty plasmid vectors that have an intact lacZ gene, allowing them to metabolize X-Gal into a blue pigment.
Step-by-step explanation:
In the context of a genetic engineering project, blue colonies on a bacterial plate indicate bacterial cells containing empty plasmid vectors. This outcome results from a blue-white screening technique where blue colonies manifest due to an intact lacZ gene that expresses beta-galactosidase, which can metabolize X-Gal thereby producing a blue color. This generally occurs when the lacZ gene has not been interrupted by the insertion of foreign DNA.
In the scenario where foreign genomic DNA was degraded by nucleases, and the plasmid vector remains intact, we would expect to see a mixture of both blue and white colonies. The blue colonies would arise from cells that contain the plasmid that religated to itself without the insertion of foreign DNA. In contrast, white colonies would indicate the presence of cells with recombinant plasmids; however, in this specific case, as the DNA was degraded, there might not be any white colonies or only a very few if some of the degraded DNA managed to integrate into the plasmid.
Therefore, the correct answer to the question 'During a genetic engineering project, which bacterial cells would produce blue colonies?' is that blue colonies represent cells containing empty plasmid vectors with no foreign DNA inserted, disrupting the lacZ gene.