DNA Structure

Now, if you guys can reach back to chemistry way back when does anybody remember what the two lines represent. To something two of something? This is a double block. Yeah? So one line is going to be a single one into the double bond. So you can see the oxygen here is double bonded to this is going to be carbon any time you ever aim that just means that it is a carbon plane. All right, and the purines these are derived from pyrimidines. So you can see the same one right here with an addition of an emerald group or this nitrogen ring out on the side. So you have adenine here and you have guanine. All right, the second compound that is in DNA is deoxyribose. So that's where part of the DNA comes from, right? The opposite of this. It is a 5 carbon sugar that helps form the phosphate backbone of the DNA. 

So this is going to do that ring and you can see it's composed of four carbons with that one oxygen on the outside and when you ask about the alcohol, this is why. It goes up into two. All right, and lastly, it has a phosphate group, which is attached to a molecule containing the carbon. So that's all this arming is over here is that it's attached to some carbon over on the side. All right, so those three components all makeup what's called a nucleotide. So this right here is going to be an image of how all of those are combined like I said, they're made up of a phosphate group, a 5-carbon sugar, which is that deoxyribose, and then the nitrogen base. So right here you can see we have the phosphate that we just talked about. That's to the carbon from the deoxyribose sugar. And then this is then attached to one of those nitrogen bases. So that is going to make up our DNA. All right, there are some important DNA characteristics. 

The DNA is held together with hydrogen bonds. And I'll show you that in just a second. It is also a double helix. Does anyone know what that means? It essentially means you have two backbones that run parallel to each other and then they are spun into the shape. DNA is always read from the 5 prime ends to the three prime ends and I'll show you what that means in just a second as well. It is anti-parallel. The adenine and guanine always bond together as do these cytosine and that should say this should be finding any enzyme always want together and try to see them walking all the responses. Okay, so we'll get on to hydrogen bonds. So like I said, it's always bonded together with hydrogen bonds so you can see our three components here on either side, this is where we have anti-parallel. 

We have one end from 5 prime to three prime rendering down. Then we are on the opposite side. You have 5 primes of three primes. So there are essentially opposite directions. So you have adding an embarrassment here, and they are bonded together with two hydrogen bonds. And then you have one size in there bonding with three hydrogen bonds. And that occurs in every situation. All right, so this is that W helix that I was talking about. Again, we can see the admin diamond. You can see the one precisely connections there. And this is just that twisting motion is going to be what makes it a double helix. All right, so the same picture again, the 5 prime to three prime. We always read DNA from the 5 prime end. So if we started up here, we would go down this way and if we start on this side right and we start reading it from the bottom and then we say, okay, it's finding that it's longing, there's that cytosine and then it's adding. 

So we get from 5 prime to three prime. Now, if you're looking at a DNA without the numbers on them, the way you would know how to label it is by this right over here. So the 5 prime end is always going to be that phosphate group. Wherever that phosphate group and use is going to be your 5 climate. And then wherever this OH is off the GRC rib roast ribose is going to be right through. So if you see a DNA molecule that is not labeled, you should know where to start by starting with that phosphate group. All right, and like I said earlier, the DNA strands are anti parallel, meaning that those two initial directions, this enables the nitrogen bases to come in contact with each other at the center. If they're both ran the same direction, then you would have the nitrogen basis in the same direction and then you would just have the center two strands of quarantine. All right, we're going to watch a short video. 

All cells require some form of instructions to be able to function properly. They need guidelines, rules, codes for making materials in the cell. And that code is a DNA. DNA stands for deoxyribonucleic acid. D for the name of the sugar in and a for nucleic acid. DNA contains the information that determines inherited characteristics. It has the code for making proteins. DNA is found in the nucleus of eukaryotic cells, and in the cytosol of prokaryotes. If we take a closer look at the chromatin inside the nucleus, we can see the structure of the DNA. The DNA has repeating subunits. And those subunits are called monomers, or nucleotide specifically. The nucleotide has three name cards, a phosphate group, a sugar, and a nitrogen base. In DNA, the name of the sugar is deoxyribose, which is part of DNA's name, and there are four nitrogen bases in DNA. 

The bases are thymine, adenine, cytosine, and guanine. Two of the bases are peering. Which have a two ring structure, and two bases are pyrimidines, which have a one ring structure. Adenine and guanine are appearing. Cytosine and thymine are pyrimidines. I remember the pyrimidines are the bases with the Y in their name, just like pyrimidine has a Y in its name. Appearing always pairs with a pyrimidine. And the slanted shape of the DNA molecule causes it to form a spiral or helix. Because DNA is double stranded, we use the phrase double helix to describe its structure. There are four scientists who are credited with discovering the shape of DNA, and they are Watson, crick, Wilkins, and Franklin. 

All of them received a Nobel Prize for their work, except for Rosalind Franklin. She died before the prize was given. Each of these scientists played a role in piecing together the structure of DNA. They learned that along the sides of the molecule was a backbone, made of alternating sugar and phosphate molecules. On the inside, like the rungs of the ladder are the nitrogen bases. Adenine and thymine form hydrogen bonds together, cytosine and guanine from hydrogen bonds together. To help me remember which base is linked together, I think of writing the letters. A and T both use straight lines, C and G use curved lines. I also know that a and T have two hydrogen bonds, but C and G have three hydrogen bonds by saying AT two, CG three. Silly things like this are actually a great memory tool. Strands of DNA are said to be complementary to one another because a will always be with T and C will always be with G based on the number of hydrogen bonds that they want to make. 

You can predict the complementary strand if you know the other strand. So let's use all of that knowledge about DNA and see if we can identify the parts of this blank DNA molecule. The easiest to label are the deoxyribose sugars and phosphates. The make complete outside of the mole. So which one is the faucet? The circle, the circle, good, and the deoxyribose. The circle, the triangle which is less than good. Joy. Deoxyribose is a Pentagon shape, and the phosphate is just a small molecule in between. Next we need to remember a rhyme, AT two, CG three. So the nucleotides with two hydrogen bonds must be a and T and the ones with three are C and G to tell which one is which you need to know that pyrimidines have one ring and purines have two. So cytosine and thymine are the pyrimidines, so they're the one-ring bases. 

Adenine and guanine are the two-ringed bases. And now you have a labeled DNA molecule. Okay, so one more question. If we are labeling this 5 prime and three prime does anybody stop which side would be the 5 prime end? Left to the right. 5, which we were being here. Yep, good for three primers being on the other. What about the bottom? Right over there, the three over two. Very good. Have one ring and puree is that episode of teacher's pet. Don't forget to like and share guys. Thanks so much.