And we have five important components. We have exxons, we have introns, we have our transcription start site, we have promoters, and we have enhancers. So let's begin by discussing what we mean by exons and introns. 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.