Hi. In this video, we're going to be talking about RNA. So RNA differs from DNA in a lot of ways, and one of the first ways that it differs is that scientists believed that RNA was actually the first genetic material used during the early world. And this is because RNA has certain qualities that DNA doesn't, and one of the major qualities is that RNA has the structure called ribozymes, and ribozymes can actually catalyze chemical reactions, meaning they can act as enzymes without anything else, just RNA completely by itself can fold into these complex structures and act as enzymes, and DNA can't do this. And so, in order for a piece of genetic material to replicate and to, you know, divide and to be expressed, you have to have proteins, you have to have enzymes that can do that. And for DNA, we have those. Right? We have DNA polymerase, which helps with replication. We have different types of transcription enzymes, and so forth, but RNA actually doesn't need any of it. It uses it because it has it, but RNA actually has ribozymes, and RNA can theoretically do all of those things without anything else. And so because of this dysfunction to form these enzymes, RNA is believed to be the primary genetic material of that early world. Now it's not as stable as DNA, and so scientists believe that eventually, you know, DNA evolved. It was more stable, so it stuck around. It became the main genetic material, but RNA was definitely likely the first type of genetic material on the planet.
And so RNA structure differs from DNA structure in that it has a ribosugar instead of a deoxyribosugar, and the difference between the two is that a ribosugar has a hydroxyl group at the 2' carbon, whereas the deoxyribose has an H at the 2' carbon. And this small difference, right, it's the presence of an oxygen or not. Right? Deoxy, so, lack of oxygen, but this small difference, this lack of oxygen, or this presence of oxygen in ribose makes RNA much more easily degraded. That oxygen makes it much easier to react with things and become degraded than DNA, which lacks that oxygen. Now for the bases, RNA contains an extra base called uracil, but it does not contain thymine. It replaces the thymine. And, RNA, unlike DNA, is normally single-stranded. So here's an example, this is a tRNA, which you may be familiar with, helps in translating proteins. But essentially, this is completely RNA. There's no protein here, and you can see that it's folded up into this unusual structure here, and the structure actually has catalytic ability. So, it can act as a tiny enzyme, essentially, to help during translation. So that gives RNA its unusual quality.
Now there are many other different types of RNAs. So mRNA is what we say is the coding RNA because this is what's used to code for proteins. There are 2 RNAs important for translation, the rRNA, which creates the ribosomes, and the tRNA, which is what I just showed you up here, and this adds amino acids onto the polypeptide chain, and we'll go over this whole process in other videos, but just sort of an overview. But interestingly enough, there are a lot of non-coding RNAs, so RNAs that don't create these tRNAs, rRNAs, or mRNAs, with a variety of functions. So we have microRNAs, which are miRNAs and siRNAs, and these play a role in what's called RNA interference. You don't necessarily need to know that, but essentially these RNAs play a major role in gene expression, turning on and turning off genes whenever they're needed or not needed. So microRNAs and siRNAs, they don't code for protein. They just exist by themselves, but they have major roles in gene expression. There are small cytoplasmic RNAs, which we know exist, but we don't know their function, and there are tons of them. No idea what they do. We have long non-coding RNAs, which again have many functions, some in gene expression, some in protein control or etcetera, some in some pathways. These could have a lot of different functions. We have snRNAs. These are important for converting pre-mRNA, so the step before this mRNA into mRNA. These are super important. And then we have snoRNAs, which process these ribosomal RNAs. So there are tons of RNAs. Right? Some code for proteins. Right? These mRNAs. Some are involved in processing. Some are involved in gene expression. Some have unknown functions even though they exist. But RNAs are super important. It's not just DNA encoding for these proteins. RNAs do a lot of the background work of the cell, making sure everything's working properly and being processed correctly so that these proteins can be expressed at the correct level that they need to be, so that we look like we do and we don't die. So RNAs are super, super, super important and have always been super important. So with that, let's now move on.
