Now, the major problem with this procedure or the initial problem that we had to solve when we were first developing this process was the following. Remember, eukaryotic mRNA molecules and prokaryotic mRNA molecules aren't the same in eukaryotic cells. The initial eukaryotic mRNA molecule that is synthesized contains introns and exons. 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.