And previously we also said that if we modify a eukaryotic gene gene in a specific way by basically removing those introns and splicing together the exons to create this modified gene and then if we introduce that gene into a bacterial cell, the bacterial cell can actually be used to produce the protein that is encoded by that eukaryotic gene. So these are two important applications of prokaryotic cells. Now, there's a problem with the second method. The second method does not always work. Why is that? Well, that's because there is another difference that exists between prokaryotic and eukaryotic cells.