If you were doing recombinant DNA with animals, why would you include a gene for GFP (green fluorescent protein) rather than AMP (ampicillin resistant)?

Answer 1

The simple answer is that using an antibiotic resistance gene as a marker in a Eukaryotic cell line would literally have no purpose. Here, what needs to be understood is WHY when doing recombinant DNA experimentation with bacteria we add the AMP gene: It's used to select bacteria that have the recombinant DNA from those that do not. Bacteria that do not have the target sequence and the AMP gene are killed by ampicillin impregnated on a selective plate. Thus, any bacteria that survives on the media has both the AMP gene and the target insertion because they are spliced in together.

Ampicillin, however, has no effect on animal cells. You can pour it all over your newly manipulated cells and select for nothing! If you add GFP as the marker, however, you can use florescence to select the cells that have the inserted target sequence AND the GFP marker.