So, bacterial viral chromosomes are much simpler. They have very different characteristics than eukaryotic chromosomes. For instance, bacterial genetic material is circular, and it's primarily just DNA. Whereas viral genetic material can be single or double-stranded, and it can be either DNA or RNA. In eukaryotes, it's usually not circular, right? It's organized into chromosomes, it's always DNA, it's always double-stranded, and much more complex than either of these two. But one of the similar things between eukaryotic DNA, and bacterial and viral DNA, is that there are DNA binding proteins that do exactly what they sound like - they bind to the DNA. The two particularly important ones in bacteria are HU and H1, and these aren't found in eukaryotic chromosomes exactly, but they're a similar protein to what we call histone proteins, which we'll talk about soon, that are found in eukaryotic chromosomes. These are super important in packaging that DNA into a small area because, even though the DNA isn't as complex, it's still a lot of DNA for such a tiny bacteria or virus, and that has to be packaged really tightly. It has to be squished together tightly, and the only way to do that is through proteins. The DNA doesn't do it by itself. So these proteins are really important in packaging that DNA. Now, a circular chromosome isn't just a circle with nothing on it; replication starts exactly what it sounds like. Right? It's where replication starts. But there are also genes on there and regulatory areas, and there are repetitive sequences, actually. Now they're much smaller in bacterial chromosomes and viral chromosomes than they are in eukaryotes, but they do have these repetitive sequences that exist. And often in bacteria, they're in intergenic regions, and these are the regions between the genes that are not transcribed. And although it's not completely known, it's believed that maybe these may act as regulatory units affecting gene expression in bacteria, very similar to how these units act actually in humans as well. So, that's just a brief overview of bacterial and viral chromosome structure. Let's now move on.