In fact, in eukaryotic cells the newly synthesized mRNA molecule consists of these intron sections, these sequences of nucleotides that do not code for any protein and they also contain these exons which were the regions that contained the codons that did code for that particular polypeptide chain. So instead of looking like this one, instead of having a continuous blue section, the mRNA molecule and eukaryotic cells, such as our own human cells consist of these intervening sections known as introns. In fact, the int means intervening sequence of nucleotides. So we have 1234 green regions, the introns in this particular mRNA and we have 12345 of these exons that contain the codons that will be used by the ribosomes to basically synthesize our polypeptide. So the major difference between these prokaryotic cells and eukaryotic cells is that our eukaryotic mrnade, once it is synthesized, it contains these introns and therefore it cannot be used directly to synthesize the proteins. It has to be modified and these introns have to be removed while the exons have to be glued, split together before that ribosome can actually synthesize the protein.