In this video, we're going to briefly compare and contrast DNA and RNA. Recall that DNA is an abbreviation for deoxyribonucleic acid. DNA's primary function is to store genetic or hereditary information inside of the cell. This is information that would be passed down from one generation to the next. We'll talk more about the functions of DNA later in our course. In this video, we're mainly going to focus on the structure of DNA. DNA forms a structure that scientists refer to as a double helix. They call it a double helix because DNA is made up of two strands, and those two strands form a helix, a twisting, winding ladder type of structure that we'll be able to see down below in our image. The two strands that make up the DNA molecule are actually antiparallel with respect to each other. "Antiparallel" means that their directionality is going in opposite directions. These two strands go in opposite directions in terms of their directionality. We'll also be able to see the antiparallel strands down below in our image. They're connected to each other via hydrogen bonds that form between the nitrogenous base pairs. So, on the left-hand side of our image over here, notice that we're showing you DNA, deoxyribonucleic acid. DNA forms a double helix structure, meaning it has two strands. You can see one strand here and the other strand here. These two strands wind onto each other, forming hydrogen bonds between the base pairs. If we were to unwind the DNA so that it has this type of structure down below, you'll see the DNA base pairs where Cs always pair with Gs and As always pair with Ts. You can see the color coordination here and see how they always pair in that fashion. This represents one DNA strand, and this down here represents the other DNA strand. You can see that this blue structure represents the sugar phosphate backbone, and we know from our last lesson video that sugar phosphate backbones of nucleic acids have directionality. Notice that this end of the sugar phosphate backbone for the strand is the 5' end, which means that the opposite end over here is going to be the 3' end. It's going from 5' to 3' left, from left to right in that direction. However, notice that the opposite strand over here, its 5' end is over here on the right, so that means its 3' end must be over here on the left. The bottom strand is going from 5' to 3' from right to left in the opposite direction as the top strand. Because we have two strands that are going in opposite directions, that makes these two strands in the DNA molecule antiparallel with respect to each other. If they were going in the same direction that would make them parallel, but because they're going in opposite directions that makes them antiparallel.

Now, on the other hand, RNA is the abbreviation for ribonucleic acid. RNA has a variety of different functions. We'll talk more about the functions of RNA later in our course. One of the primary functions of RNA is to act as a template for synthesizing or building proteins. In terms of the structure of RNA, RNA usually forms a single-stranded nucleotide chain rather than forming a double helix like DNA. So, if we take a look at our image over here on the right-hand side, notice that we're showing you RNA, which is usually a single-stranded structure. You can see the single strand of RNA right here. The single-stranded RNA will have a sugar phosphate backbone that has directionality. If this is the 3' end over here, that means the opposite end must be the 5' end. RNA specifically uses nitrogenous bases of Us instead of using the nitrogenous bases of Ts like DNA. So, T is specific for DNA, whereas Us are specific for RNA. RNA is normally a single-stranded structure, but base pairing can still apply if it binds to itself. Sometimes RNA can fold up onto itself and bind to itself, forming complex structures. Also, RNA can sometimes bind to small anticodons, which again we'll talk a lot more about later in our course. You can see that this is how the RNA would base pair in the same way as DNA, except replacing the T with the U, and that's really the main takeaway. This concludes our introduction to the differences between DNA and RNA, and we'll get some practice applying these concepts as we move forward in our course. I'll see you all in our next video.