So if we are to use bacterial cells to form different types of eukaryotic proteins from Eukaryotic genes we have to first remove these introns from the genes of those Eukaryotic DNA molecules. So once again Eukaryotic genes contain noncoding segments called introns. And when Eukaryotic genes are transcribed the pre mRNA molecule that is formed contains those intron segments. What happens inside the eukaryotic cells is these intron segments are removed because the eukaryotic cells contain the proper proteins and the proper machinery inside the cell to actually carry out the process. But this does not exist inside prokaryotic cells such as bacterial cells. And this is a problem because if we take a Eukaryotic gene so let's suppose this is Eukaryotic DNA molecule and this colored portion is the gene within that eukaryotic DNA molecule that codes for some particular protein.