to confirm that the selection marker is integrated into the correct place in the genome, sometimes a negative selection is used in addition to the standard positive selection marker. which of the following would act as a negative selection marker? group of answer choices transforming the cells with two different knock-out cassettes, each containing the same selection marker. a second marker in the knock-out cassette, that if inserted into the genome results in cell death when plated on the selective media. a second marker inserted into the transformed cassette is now required to grow on the selective media. transformation of a different gene, which does not act as a selection marker, to replace the gene of interest.