In this video, we're going to briefly compare and contrast DNA and RNA. Recall that DNA is an abbreviation for deoxyribonucleic acid. Its 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 antiparallel with respect to each other. "Antiparallel" means that the directionality is going in opposite directions. These two strands go in opposite directions in terms of their directionality. We'll be able to see the antiparallel strands as well down below in our image. The two antiparallel strands are connected to each other via hydrogen bonds that form between the nitrogenous base pairs. Once again, we'll be able to see this down below in our image. On the left-hand side of our image over here, notice that we're showing you DNA. DNA forms a double helix structure. It has two strands. You can see one strand is right here and the other strand is right here. These two strands wind up onto each other, forming hydrogen bonds between the base pairs. If we were to unwind the DNA, you'll see the DNA base pairs where C's always pair with G's and A's always pair with T's. You can see the color coordination here and see how they always pair in that fashion. This here 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 the 3' end. It's going from 5' to 3' from left to right in that direction. However, notice that the opposite strand over here, its 5' end is on the right, and so that means its 3' end must be 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 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 going in opposite directions makes them antiparallel.
On the other hand, RNA is the abbreviation for ribonucleic acid. RNA turns out to have a variety of different functions, which we'll talk more about 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, it usually forms a single-stranded nucleotide chain rather than forming a double helix like DNA. 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 has 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. You can see that RNA specifically uses nitrogenous bases of U instead of T like DNA. T is specific for DNA, whereas U's are specific for RNA. Normally a single-stranded structure, RNA can sometimes fold up onto itself and bind to itself forming these complex structures. Also, RNA can sometimes bind to small anticodons, which again we'll talk a lot more about later in our course. But 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 here concludes our introduction to the differences between DNA and RNA, and we'll be able to get some practice applying these concepts as we move forward in our course. I'll see you all in our next video.
