Organization of DNA in the Cell

by Jason Amores Sumpter
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so recall from our previous lesson video that before any cell can divide, it must first replicate or duplicate or make an extra copy of its d N A. And so how the DNA is organized in the cell is very important. And in this video we're going to introduce the organization of DNA in the cell and which will notices throughout this video. We're going to introduce a whole bunch of different terms and notice that the terms that link directly to the image down below are labeled with these letters, and we have letters A, B, C, D and E. And once again, these letters labeling specific terms are going to link directly to the letters that we have down below in our image. And so keep that in mind as we go through this video. And so the very first term that we're going to introduce here is a term called the genome, and the genome refers to the complete set of all of a cell's DNA. And all here is the key word. Now the genetic material is referring to molecules that determined the inherited traits of an organism, and usually when scientists use the term genetic material. They're referring to the D N A of the organism. Now, within a cell, the DNA is going to associate with proteins that air called his stones. And these his stone proteins are going to form units that air called nucleus zones. And so the nucleus OEMs themselves can be can be defined as units of eight, his stone proteins at the core with DNA wrapped around it. And so to start, to understand these terms, let's take a look at our image down below. And so we'll start here with term A the genetic material DNA. And so notice here, we're showing you an image of DNA as we've discussed it in our previous lesson. Videos. Ah, double stranded helix of nucleotides. As we see now within a cell. It turns out that the DNA is going to be organized into thes units called nucleus OEMs, and the nuclear ISMs form when DNA is wrapped around thes hissed own proteins. And so notice these little purple circles that you see throughout our Histon thes histon proteins. And the Histon proteins will organize into, uh, these units of eight Histon proteins. Andi, The Histon proteins formed the core of the nucleus zone and DNA will wrap itself around the hist own protein, almost like taking a core of ah, pencil or a pen. If that was the hist own core and taking a ah yarn and wrapping the yarn around the hiss stone protein. That's basically what the nuclear zone consists of histon proteins at the core with DNA wrapped around it. Now it turns out that within the cell, these nuclear zones can actually take different forms, depending on if the cell is actually in a non dividing state or if the cell is in a dividing state. And so when the cell is in a non dividing state when the cell is not dividing, it turns out that the DNA in the nucleus homes are going to be organized into what's known as chroma tin. And so Chroma tin represents loosely packed or coiled nuclear ISMs and non dividing cells. But when the cell is about to divide in a dividing cell, the nuclear zones take a different form, and they're no longer loosely packed or coiled. Instead, they're going to become tightly packed into what are known as chromosomes, and so crow. Metin refers to loosely packed or coiled nucleus homes in a non dividing cell and chromosomes is referring to tightly packed or highly condensed nucleus OEMs in a dividing self. And so let's take a look at our image down below to get a better idea of this. And so notice on the left hand side over here, what we're showing you is a non dividing cell. And so notice that within the nucleus of this non dividing cell when you zoom in here, the DNA is organized in this format here, where the genetic material, the DNA is wrapped around his stone proteins to form these nucleus homes and these nuclear zone sub units, these nuclear is, um, units here, uh, when the cells in a non dividing state it's going to be in a loosely coiled state called chroma eaten. And so over here, in the non dividing state, the DNA is in a crow Metin form, and the crow misinform because it's so loosely coiled. You can really think of a ball of yarn that is really loosely coiled and so notice that we have this loosely coiled ball of yarn here or bunch of yard. But notice that over here on the right hand side, what we have is the dividing cell and notice that the dividing so the DNA is going to condense. And so we have condensing DNA here, and the DNA condenses into highly condensed or tightly packed chromosomes. And so, really, this term chromosomes, you could think of a ball of yarn that is really, really tightly coiled, nicely wrapped around, unlike the ball of yarn that's over here. And so the term chroma 10 and chromosomes are both preferring to DNA wrapped around protein. And the difference is really that Crow Metin is going to be, um, or loose form of the DNA found in non dividing cells, whereas chromosomes are going to be mawr tightly coiled DNA that air found in dividing cells. And so this is going to be very, very important, this condensing of the DNA into chromosomes. It's going to be very important for moving the DNA around within a cell that is dividing, and so we'll get to talk a lot more about chromosomes and the dividing cell as we move forward in our course here. But for now, this here concludes our introduction to the organization of the DNA in the cell, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.