Genomes and Genome Evolution

by Jason Amores Sumpter
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hi. In this video, we're going to talk about genomes, how they evolve and what they're made of aside from jeans. So the pro carry ah tick genome, for example, is mostly uninterrupted coding sequences, so that's just uninterrupted sequences of DNA that codes for proteins. There's very little space between the genes and very few regulatory sequences mixed in that genome. The Eukaryotic genome, on the other hand, has huge amounts of non coding. DNA, or N C DNA has many repeated sequences, and it's just much larger and has mawr genes than pro carry its meaning. It needs more regulatory sequences to, but if you actually take a look at this graph right here, you'll notice that pro Kerasiotes on the Y axis. We have the number of protein coding genes on the X axis. We have genome size and pro carry outs. The number of genes and the genome size has a linear relationship. You can see the red here, those air, all the points representing pro carry outs, and it basically makes a straight line, meaning as we increase the number of genes, we're going to proportionally increase the size of the genome in a pro Cariou, you carry outs. On the other hand, we gotta make things complicated, right? So for you Kerasiotes, which are marked as thes little green dots. In this graph, you'll notice that there's huge variation between number of genes and the actual size of the genome. I mean, there are green points all the way out here. There's a bunch up here, and also, if you were to draw a line through this, you'd see that it kind of has a curved to it. This is not a linear relationship between number of coding genes and genomes size Now. How do genomes evolve? Well, one of the ways genomes can evolve is through something called lateral gene transfer. Sometimes this is called horizontal gene transfer, and this is just when jeans transfer from one organism to another through a method that's not reproduction. So we've actually learned about one type of lateral gene transfer already, and that's transformation. What bacteria do when they pick up foreign DNA and incorporate it into their genome. That's lateral gene transfer, and you can see that happening right here in our tree of life are file a genetic tree, which we'll talk about Maurin later video. So here we have genes transferring from one branch over here to another branch over here that is lateral gene transfer. Now, lateral gene transfer can also occur in eukaryotes, though its's mostly common. It's most common bacteria that ISS now. Some pieces of DNA are very ancient, and we actually we call these conserved arrangements of DNA in related genomes. We refer to this relationship as sin, tinny, and Centanni is very useful when determining evolutionary relationships between organisms. You look at these conserved arrangements of DNA these conserved sequences, and it allows you to tell how far to species have diverged from each other. How far two very distantly related organisms have diverged from each other. Now, another way that genomes can evolve is through chromosome duplication. And usually when we get the wrong number of chromosomes, this is a really bad thing. It's deleterious. However, there are instances where chromosome duplications have actually led to the evolution of jeans, and we'll talk about this later when we talk about speciation or the formation of new species. Now, another way that genomes can evolve is through Exon shuffling, and this is where literally the Exxon's in a gene get shuffled around, and this can lead to novel proteins to brand new proteins. It can also lead existing proteins to develop new functions. And in addition to Exon, shuffling deletions can do the same thing. Removing pieces of genes can also lead Thio brand new proteins and brand new protein functions, so there are many ways that genomes can evolve. However, it's worth noting that most mutations that occur are not beneficial, right. It's the rare mutation that is actually beneficial and can lead to some increased fitness of an organism that, let's turn the page.