Practice Test 6

A lab uses PCR to confirm the presence of a transgene in a mouse line. Primers are designed with one primer in the transgene and the other primer in adjacent mouse genomic sequence at the insertion site. Only transgenic mice produce a PCR band.

Which result would be expected if PCR is applied correctly in this context?

Researchers clone a human cytokine cDNA into a bacterial expression plasmid under an inducible promoter. After transformation into E. coli, colonies are grown with and without inducer. Protein levels are assessed by SDS-PAGE and immunoblotting with an anti-cytokine antibody.

Observation: A strong cytokine band appears only in induced cultures of transformed bacteria; no cytokine band appears in uninduced cultures or in induced cultures transformed with empty vector.

Which outcome is most consistent with the use of gene cloning in this context?