So, in any eukaryotic gene, we have those segments of DNA that actually do code for a polypeptide, and those segments that do not code for a polypeptide. So in this particular diagram, these are the exons, they are segments of DNA that do code for a polypeptide. While these orange sections are the introns, they do not code for anything useful. And eventually, during the process of RNA splicing, these sections are actually removed from that mRNA molecule and only these exons are actually left. Now, what about this segment right over here? So this green segment is known as the transcription start side, and this is where transcription actually begins.