 Hey everybody, Dr. O here. We're going to talk a lot about DNA and RNA in the next chapter, but for this chapter we're just going to talk about the basic biochemistry here. So what is DNA and RNA made up? So real quick, DNA is going to be this genetics information storage device that's in the nucleus of your cells. And RNA is going to be how that message gets from the nucleus inside your cells to the ribosomes where proteins are actually produced. You have two meters of DNA inside of every cell of your body that has a nucleus, so some cells don't have nuclei, 3 billion base pairs, so about 6 billion bases. There are somewhere in the neighborhood of 23,500 coding genes that are found on your 46 chromosomes, 23 you got from mom, 23 you got from dad. About 1% of your cell is DNA, there's somewhere in the neighborhood of 6 picograms of DNA. That's what's amazing about DNA, there's 2 meters of it, but you only have 6 picograms worth of it. You know, if you stretched all your DNA out, it would go to the sun and back several hundred times. Not so much DNA is crammed into you, but in a very tiny package. Where it versus RNA, so RNA is going to be about 5% of your cell, it's going to be 10 to 30 picograms, so there is more RNA than there is DNA inside your cells. Any one cell can have somewhere over 300,000 different RNA messages floating around inside at the same time, thousands of different types of RNA. So both are very important, let's just go ahead and look at the structure here. So they both, what they have in common is they both are built on a sugar phosphate backbone and they both have these nitrogenous bases or nitrogen containing bases in them. So you see that there are 5 of these nitrogenous bases. You have the pyrimidines, cytosine, thymine, and uracil, and how you remember that is cut the pie, CUT, cytosine, uracil, thymine, cut the pie, Py is how you remember the pyrimidines, and you have the two purines, adenine and guanine, how you remember that, pure as gold, so purines, adenine and guanine. So these 5 nitrogenous bases, A, G, C, T, and U, are called nitrogenous bases. When you add them to the sugar phosphate backbone, they're now called nucleotides. So both DNA and RNA are made of nucleotides, they both have a sugar phosphate backbone. So the sugar that makes up DNA is called deoxyribose, which is why DNA is deoxyribonucleic acid, because it's the name of the sugar. The sugar that makes up the sugar phosphate backbone of RNA is called ribose, which is why RNA is ribonucleic acid. So those are the sugars that make them up. As far as the nucleotides themselves or the bases, DNA is made of A, C, G, and T. RNA is made of A, C, G, and U. So thymine is replaced by its cousin, uracil, when you make RNA. Last thing to note about the key differences between the two, DNA is double-stranded. You see this, this here is the double helix, looks like a rope ladder twisted on itself. So DNA is double-stranded, made of A, C, G, and T, and the sugar is deoxyribose. RNA is going to be single-stranded, made of A, C, G, and U, and the sugar in that backbone is ribose. I think that's all the important information for now. We will go into DNA replication, transcription, and translation in the next chapter. I hope this helps, have a wonderful day, be blessed.