Hi. In this video, we're going to be talking about types of mutation. So, I really wish that this would be super fun to go over, but it's really not. It's just a ton of vocabulary of different types of mutations and how they affect different things. And so, I've tried to organize it so that it's in some kind of order, but generally, it's just going to be this video, and then the one that follows is going to be just a bunch of vocabulary words that you need to memorize. The good point is that most of them are common sense. They make sense of why they're named that way, so hopefully, it won't be too hard to remember them.
This is about mutations, and there are many different types of mutations. One way to describe them is how they arise. The two ways that they can arise are spontaneously, meaning they just occur sort of randomly, or induced, meaning that something has caused them. Spontaneous mutations are those random occurrences. Things like DNA replication just randomly have errors occasionally. That's a type of spontaneous mutation. An induced mutation is something that's caused, and these can occur via natural ways or artificial agents, and so these can occur by scientists in the laboratory inducing mutations. They can also come from different types of UV radiation for instance in the sun. Those are induced mutations because they're caused by something that isn't just a random occurrence.
Now a second way to classify mutations is where the mutation occurs, and so we have somatic cell mutations, which of course, occur in somatic cells, and germ cell mutations that occur in germ cells. And this is a really important part because somatic cell mutations only affect the organism itself. It doesn't affect the offspring at all. But if the mutation occurs in the germ cells, so the sperm and the egg, that means that it's going to be passed on from generation to generation. So obviously, these germ cell mutations have a lot more ability to severely affect multiple generations, whereas somatic cell mutations generally only affect the individual that has that mutation. Here's just a picture, if you have a somatic cell, you have a mutation here in red that's not going to be passed off, whereas a germ cell, you have the same mutation, it will be passed on to offspring.
Now, the first type of mutation I really want to talk about is a point mutation, and this is a mutation that occurs in one single nucleotide. There are many different types of point mutations, and this is where it starts getting vocabulary heavy where it's not necessarily, you know, intuitive. Right? Somatic and germ cell mutations, that makes sense, but some of these terms you may have never heard before. So the first type the first class of point mutation is a base substitution, meaning that you're substituting one base for another. So, you're changing one base into another. And there are 2 types, you have transitions. This replaces the base with one from a similar category, so this would be purine to purine, or it could be pyrimidine to pyrimidine. And then you have transversions, which is the opposite. So you do purine to pyrimidine or pyrimidine to purine. Right? So those are the two differences, but essentially, you get one base, you have one base, it's supposed to be the right base, it's mutated, and that changes it for another base.
Then you have base insertion, which is the second class, and base deletions, which is the third class, and they do exactly what they sound like they'll do. Insertions add nucleotides, and deletions remove them. You can have mutations called an indel mutation where an insertion and a deletion occur at the same time. Now if there's 1 insertion of 1 nucleotide and a deletion of 1 nucleotide, that's not going to change the length of the sequence of the gene, but there can be an insertion of 3 nucleotides and a deletion of 18, and then that changes the length of the gene that's being mutated, and base insertion and deletions easily affect codons. Now remember codons are those 3 nucleotide sequences. So if you delete this one, then you have now made this the second position and this one the fourth, and that drastically can affect codons and how they're read.
So here we have an example, if you switch a purine to a purine, that's called a transition. But if you mutate a purine, or so an a to a c, which is pyrimidine, that's called the transversion. So you can see that different ways that this happens causes different things where transversions are in red and transitions are in blue.
So a third way to classify mutations is their effect on codons, which is what I said before. Now remember, codons, those three nucleotide code. Now, a mutation can be called silent or synonymous, depending on the book that you use if that mutation changes a codon to another codon, but that codon codes for the same amino acid. So remember, there's a bunch of different codons that code for the same amino acid. So if you just switch out the nucleotides, but those nucleotides still code for the same amino acid, it's not going to affect the protein because the same amino acid is produced. So we call that a silent mutation because it is a mutation, a nucleotide has been changed. It has no effect on the protein and therefore is silent. We have missense mutations and this is a change in a codon that changes that codon to one that codes for a different amino acid. So missense was the same amino acid, missense is going to be for a different amino acid, and there are 2 types of these. There's conservative and nonconservative. Conservative changes the codon to another codon with a similar chemical nature. So if you have it, it originally coded for a hydrophobic codon, or hydrophobic amino acid, and a missense mutation would be if it changed the amino acid, but it did it to another hydrophobic. So you can remain the chemical property even though the amino acid is different. Nonconservative is more severe because the codon is changing to another codon, but it's of a different, or chemically different amino acid. So if you have to change a codon, right, if it is a missense mutation and the codon is actually changing to a different codon and that's coding for a different amino acid, would you want one that's more similar or one that's more different? Right. If you're a gene producing a protein, you want one more similar because you want to retain as much as possible with this mutation, the chemical nature that it's supposed to be. So conservative missense mutations are generally less severe than nonconservative ones.
Now, their type is a nonsense mutation. This changes a codon to a stop codon. Obviously, that's it, you know, if a stop codon appears right in the middle of the gene, then that's going to only produce the first half of that protein, it's not going to be functional, it's probably going to get degraded, and that's not going to be good. You're not going to want that. It's not it's really going to harm the phenotype of the organism. And then finally, we have frameshift mutations, and this is where the codon alters the reading frame. So, if the reading frame is this, 123123, a frameshift mutation would mark out somehow deleting 2. Right? So now your codons are 131, 23123, and then something here. Right? Back up so you can see that. Now this 123123123 is going to code for something completely different than 13123123. Right? So frameshift mutations alter the codon reading frame, and that alters the amino acids that are produced, forming the protein. So here we have this, some different examples of point mutations. Here's the silent one. You can see that the normal is going to be TTA, and now it switched to TTT, and now it switched it to AAA. And it doesn't really matter because both of these encode for lysine, so lysine will still be produced. If, or the normal is TTC, and then it switched it to TTT. This is the RNA. Now, the nonsense mutation takes this normal TTC and changes it to ATC. This encodes for a UAG, which is a stop codon. It's going to mess up the protein, up very badly. Then you have missense with conservative and nonconservative. So a conservative is it changes the codon, changes the amino acid, so it went from lysine to arginine, but this arginine has a similar chemical structure. So you can see that it's kind of represented by this purple color here, Whereas the nonconservative changes the amino acid, but it does so in a completely different way, whereas these are basic. I know that because here, and this is polar. And these are completely different chemical structures which will affect the protein's composition and structure. So, that is kind of a set, like I said there's going to be a lot of vocabulary, there's going to be a lot of vocabulary in the next video too, but this is kind of the first set of understanding the different types of mutations.
So, with that, let's now turn the page.
