And that can be a very useful procedure. For example, we can use this as a marker to basically differentiate between those cells that did not take up the plasmid and a cell that did take up the plasmid. So let's suppose we have a bunch of cells in our solution and we essentially introduce this plasmid into our cells. Now, some of the cells will take up that plasmid, but some cells will not take up the plasma. Now, those cells that did take up this plasmid will now have the ability to resist this tetracycline antibiotic because they'll have the gene for it. But those bacterial cells that did not take up this plasma will not have that ability to resist a tetracycline.