Aresearcher is preparing to insert a human gene of interest into a bacterial plasmid in order to clone the human gene. she has genetically engineered the plasmid to carry a gene that confers resistance to the antibiotic ampicillin, which she will include in the plating medium when she grows the recombinant bacteria. why has she engineered the plasmid to include an antibiotic resistance gene? a. recombinant cells are vulnerable to infection and require antibiotics. b. the antibiotic resistance gene will the bacterial clones metabolize sugar in the medium. c. she will be able to recognize bacteria that have taken up the plasmid because they will be able to survive in the presence of ampicillin. d. the antibiotic resistance gene will produce a blue color, enabling her to recognize recombinant bacteria.

The correct answer is C

Explanation:

Bacteria can take up DNA from other bacteria and from the environment in a process called transformation. This process allow bacteria to incorporate foreign DNA inside their own genetic material. This foreign DNA could be for example a plasmid.

A plasmid is a tiny loop of DNA present in a bacterial cell. They grow and exist apart from the bacterial DNA, and this is why they can replicate independently. This feature allows researchers to use them as cloning vectors. Researchers can “paste” a gen of their choice inside a plasmid using special enzymes, this plasmid would replicate inside the cell expresing the gene the researcher wanted.

The plasmid that the researcher engineered in this case, included an antibiotic resistance gene to ampicillin. This means that a bacteria without the engineered plasmid would die in the presence of this antibiotic. So, the way she can find out which bacteria took up a plasmid inside their DNA is to add the ampicillin to the plate and see if some bacteria survived.  

If the plasmid is successfully transferred to the bacteria, it will have the ability to survive in ampicillin and the researcher would be able to see bacteria in the plate. On the other hand, the bacteria that didn't integrate the plasmid in their genetic material, would eventually die and that would mean they are not able to survive in an environment with the antibiotic.