Organization of DNA in the Cell - Video Tutorials & Practice Problems

Organization of DNA in the Cell

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.

A collection of DNA and associated proteins in a cell defines the term:

a) Sister Chromatids.

b) Centromere.

c) Chromatin.

d) Chromosome.

• A. Sister Chromatids.
• B. Centromere.
• C. Chromatin.
• D. Chromosome.

Choose the option that correctly lists the following genetic material in a dividing cell from smallest to largest.

• A. DNA, Chromatin, Nucleosomes, Chromosomes.
• B. Chromatin, Nucleosomes, Chromosomes, DNA.
• C. DNA, Nucleosomes, Chromatin, Chromosomes.
• D. Chromosomes, Chromatin, Nucleosomes, DNA.

DNA Replication

in this video, we're going to begin our introduction to DNA replication. But later in our course and a different video, we're going to go into a lot more details of DNA replication where we'll talk about all of the enzymes and all of the steps involved with DNA replication. But again, that's not what we're going to do in this video. We're not going to go into that much detail and this video we're on Lee going to cover the basics of DNA replication, and we're going to introduce some terms that are going to be helpful for you as you move forward in our course, learning about cell division now recall from our previous lesson videos that before any cell can divide, the DNA must first be replicated. And it's important to be able to recognize different synonyms for DNA replication because your professors in your textbooks will sometimes use different words. Toe represent the same exact thing as DNA replication, and so DNA replication can also be described as DNA synthesis or the DNA being synthesized. Or it can also be defined as DNA duplication or the DNA being duplicated. But really DNA replication, DNA synthesis and DNA duplication are all referring to the same thing. And so DNA replication is referring to the process that produces an exact copy of all of the cells DNA. And so the reason that the cell would want to produce an exact copy of all of its DNA is in preparation for cell division, because again, before any cell can divide, this DNA must be replicated so that the cell has an exact copy of the DNA, and each of the resulting daughter Cells from cell division can each get their own copy of the DNA. Now, DNA replication is going to convert what are known as unrepresented chromosomes that have not yet been replicated into replicated chromosomes that have been replicated after DNA replication. And these replicated chromosomes have to identical Sister Crowe motives. Now the sister part here is just referring to the fact that these promoted are identical toe one another. They're exactly the same, and the term chrome it'd is really just defined as half of a replicated chromosome. And so, within a replicated chromosome, there are two chrome attitudes, and they're going to be identical to one another. And that's why they're referred to a Sister Crowe motives. And so, within a replicated chromosome again, there are two chrome attitudes. And, uh, these two Chromatis, they're going to be joined to one another at a position called the Centrum Ear, which is pretty much like the waste position of a chromosome, and we'll be able to see that down below in our image. Now notice. Over here on the left hand side, we're showing you an image of a single unrepresented chromosome that has not yet been replicated. This is what the chromosome would look like before DNA replication, and it is going to be referred to as a chromosome or specifically, an unrepresented chromosome. Now, technically, this single unrepresented chromosome would only have one chroma tid. But we have chrome. It'd here and quotes here because the textbooks won't refer to it as a single chrome. It'd they'll just refer to it as a single unrepresented chromosome. And so that's why we have this guy here from Austin Powers here with the quotes around the chrome. It'd just reminding you that this is really a single unrepresented chromosome. Uh, it would only have one promoted, if that's the way that the text books would use that terminology. But again, this is what the chromosome looks like Before DNA replication noticed that after DNA replication represented by this arrow right here, that the chromosome looks different and that here what we have is still a single chromosome. But it's no longer an unrepresented chromosome. It's now a single replicated chromosome. And so notice that, uh, it has the single replicated chromosome. No, doesn't just have one chrome, it'd it now has to crow motives. And so that's what we're saying down below here is that now there are two identical chroma tits. This right here is one promoted. And this over here is the second crow matted, and these two chromatic are identical toe one another. And that's why they're referred to as sister Chromatic IDs and notice that the sister chromatic are joined together at this position. That's right here, which is really like the waste position of the chromosome. Um, and it's called the Centrum ear. And so really, you can tell if a chromosome has undergone DNA replication or not, just by looking to see how maney chroma Tibbs it has. If it has to crow motives. Basically, if it looks like this. If it looks like an X, if you will, then you know that it's going to be a replicated chromosome. But if it does not look like an X, then you know that it is an unrepresented chromosome. And so this year concludes our brief introduction to how DNA replication converts unrepresented chromosomes into replicated chromosomes with two identical Sister Crowe motives, 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.

The structures labeled Y in the image below are called:

• A. Centromeres.
• B. Centrioles.
• C. Sister chromatids.
• D. Spindles.