And so before that mRNA molecule is used, those introns have to be removed and the exons have to be spliced together. And the prokaryotic cell simply doesn't have the cell machinery to actually carry out that process because prokaryotic mRNA always only contains the exons, never the introns. So the complication with using eukaryotic DNA in prokaryotic cells is that these prokaryotic cells, bacterial cells, do not have the proper cell machinery to modify the pre mRNA produced from eukaryotic genes. For instance, eukaryotic mRNA contains exxons that must be spliced out and that prokaryotic cell cannot carry out the splicing process. So how can we solve this problem? How did we solve the problem?