And what that means is the second method described here, producing eukaryotic proteins by introducing eukaryotic genes into prokaryotic cells cannot be done for all eukaryotic proteins because of what we just described. And that leads us directly to the next question. Can we actually introduce foreign eukaryotic genes into other eukaryotic cells? So instead of using prokaryotic cells to produce a desired eukaryotic protein, can we use eukaryotic cells, for example, animal cells, to actually produce copies of proteins that extract the proteins and use those proteins for a variety of different purposes? So it turns out that we can actually introduce recombinant DNA molecules, foreign DNA molecules, into certain eukaryotic cells, such as, for example, malcells, as we'll see in just a moment. And then these genes can basically use to express proteins, produce different types of proteins.