In this video, we're going to talk a little bit more about the detailed DNA structure. First, it's helpful to recall the information that we covered about DNA in our previous lesson videos where we first introduced DNA. If you don't know anything about DNA structure, then please be sure to go back and check out those older videos on DNA before continuing here. Now that being said, recall from those older videos that DNA actually consists of two strands of nucleotide monomers or these nucleotide building blocks that are repetitively linked together. If you take a look at our image down below, notice that we're showing you three different representations of the DNA molecule. We've got one representation of the DNA molecule over here, another representation of DNA here in the middle, and a third representation of the DNA molecule over here on the right. Previously, in our previous lesson videos, we had shown that DNA forms a double helix where there are two strands, one strand there and another strand here, that are wrapped around each other and twisted upon each other to create a double helix, this twisting ladder type, formation. But if you were to take this DNA, double helix and you were to untwist the DNA double helix so that it's a straight formation, it would look something like what you see here. And then if you were to zoom into this structure, then you would get this image right here, a more detailed view of the DNA molecule. Again, what you would notice is that the DNA molecule consists of these nucleotides that are repetitively linked together. So here is one nucleotide. This is one nucleotide here. This is another nucleotide here. Here is another nucleotide. These nucleotides are just repetitively linked together to create a DNA strand. We have two DNA strands here. We have one DNA strand right here, and then we have a second DNA strand over here. Notice that these two DNA strands are both made up of nucleotides, and they are connected to each other via these hydrogen bonds that form between the nitrogenous bases. Here we can label these dotted lines as hydrogen bonds that form between the two strands and that connect and keep the two strands held together. Recall from our previous lesson videos that a single nucleotide consists of three components: a phosphate group, a 5-carbon sugar, and a nitrogenous base, either adenine, guanine, thymine, or cytosine, abbreviated as A, G, T, or C. Also, again, recall that these two DNA strands are antiparallel with respect to each other, which means that they go in opposite directions in terms of their 5' prime and 3' prime ends. You can see that this strand over here on the left is going from 5' prime to 3' prime, top to bottom. However, this other strand over here on the right is going from 5' prime to 3' prime in the opposite direction from bottom to top. The DNA strands are going to be antiparallel. When you compare the 5' prime end to the 3' prime end, what you'll notice is that at the 5' prime end of each strand is a free phosphate group. At the 3' prime end of each strand is a free hydroxyl group. What you'll note is that when we take a look at the 5' prime end, again over here, there is a free phosphate group or a phosphate group that is not linked to another nucleotide. Whereas this new phosphate group is not free because it's attached here to two nucleotides. But this is a free phosphate group, and notice that both 5' prime ends have a free phosphate group. Then notice, again, at the 3' prime end, you'll have a free hydroxyl group or a free OH group, And, that applies for both, 3' prime ends. What you'll notice is that here comparing the same sides of the two strands, that they are chemically different. One has a free phosphate group, and one has a free hydroxyl group. That's why it's important to keep in mind the directionality of these DNA strands in terms of their 5' prime and 3' prime ends, and that'll be very important as we move forward in our course and talk about DNA replication. What you'll notice here is that the nitrogenous bases are kind of toward the middle of the DNA molecule and on the perimeter of the molecule is the sugar phosphate backbone. They call it the sugar phosphate backbone because it's a repetitive repeat of sugar phosphate, sugar phosphate group, sugar, phosphate group, sugar, phosphate group, and so on. DNA molecules will have a sugar phosphate backbone. That's why we represent that sugar phosphate backbone here, using these blue lines. This here concludes our brief introduction to some of the detailed DNA structure, and we'll be able to get some practice applying these concepts that we've learned as we move forward in our course. So I'll see you all in our next video.
Table of contents
- 1. Introduction to Biology2h 40m
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- 3. Water1h 26m
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- 6. The Membrane2h 31m
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- 14. DNA Synthesis2h 27m
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- Review of the Lac Operon & Trp Operon11m
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- 42. Osmoregulation and Excretion50m
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- Introduction to Terrestrial Biomes10m
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- Terrestrial Biomes: Northern Regions15m
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- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
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- Population Sampling Methods23m
- Life History12m
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- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
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- Logistic Population Growth32m
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- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
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- 52. Ecosystems2h 36m
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14. DNA Synthesis
Discovering the Structure of DNA
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