Hi in this video we're gonna be talking about gal regulation. So your books likes to use this example of the gal gene regulation as an example of gene regulation in lower eukaryotic cells. So things like yeast which is where the gal system is um exists. So the gal gene system, what it is it kind of reminds me of the opera Ron's in pro charismatic cells but there are differences because operations are very much a pro carry ah tick way of regulating. But the gal gene system pretty much produces jeans that transport and break down or process or whatever you want to put here. This sugar called galactose and like I said before we're focusing on yeast cells. So um this system is given a fancy name and that fancy name is called induce a ble. And the reason that it's given this induce a ble title is because the gal genes are regulated by the presence or absence of galactose sugar. So I guess that this very sounds very much similar to lack operation or the trip operation which we talked about in the pro carry on gene regulation chapter. But this is eukaryotic so it is a little different. So I'm gonna give you the summary here and then we'll explain why this is so if there's no galactose no transcription occurs if there is galactose transcription control it happens. And so this type of regulation is called positive control because if it's present it's activated. So how does this happen? So here's your summary let's now get into the details. So the transcription is controlled by a specific region upstream. So before the gene start side of the gal genes called the U. A. S. Region. And what happens is a protein that's encoded later called gal four will bind to this U. A. S. Region at four different sites. And so the second protein you need to know about is gal ABP. And this negatively regulates the gal four. So gal for gene which makes the gal for approaching. So if it's all upper case that's gonna be gene. If it has lower case in it this is gonna be protein. So don't get confused because here we're talking about protein here we're talking about the gene. So what happens with these proteins? So if you have no galactose there's an absence of galactose. This protein binds to this protein and prevents transcription. If you have galactose galactose interacts with another protein called gal three which binds to this U. A. S. Gal four and promotes transcription. So let's look at this, let me back up. So here we have D. N. A. Here's your US sequence and here's your gal genes. Like I said this looks kind of like a bacterial opera on. So transcription doesn't occur, glucose isn't available because gal for protein binds to the gal 80 protein that binds to this U.A.S. region. And this blocks transcription. If galactose and gal three are now available which is here what happens is the gal 80 leaves. And now gal four. This comes in swoops in gal four is here. This is active. So you get transcription of these jeans and this makes sense right? Because the gal genes are responsible for processing galactose and you only need to process galactose if you have it. So when galactose is available you need these genes and when it's not available you don't need to waste the energy producing these jeans because they're not gonna do anything because there's no black toast there. So that is an example of gene regulation in eukaryotic cells but more lower eukaryotic cells like yeast. So that let's now move on.