Hi in this video I'm going to be talking about episode Asus and complementation. So I get it's a little out of order. But I'm actually going to talk about complementation first. So a complementation test is performed in order to determine if two mutants with the same phenotype have mutations in the same gene. So if you do this huge like cross or this huge experiment with flies for instance and you have thousands of them and you come across a couple with the same gene or the same phenotype. They all have really short legs for instance. So you can do a complementation test where you make them together to figure out whether or not those short legs mutations that you find are all in the same gene. Like a short like gene or if there are mutations in multiple genes causing the same genotype. So how you perform a complementation test is you take the two mutants that you have and if they are excessive you can make them together. And when you do that the offspring are wild type meaning that they have long legs, they don't have that short like phenotype. Then the two mutations are in different genes. If they're mutant that means the two mutations are in the same genes. Same genes not different. Same now sorry about that. I will go back and edit that. So it's clear in your handout but just know these are in the same genes now. Um Why is that the case? Well because if you have to immune say um Butin one and 2 and here's their mutations. If they're in the same genes when you do this cross you're gonna get them all with mutants right? That's what the cross is gonna look like. But if instead it's in two different genes. So what this would look like is this you would have R. R. And you have S. S. And little s little s. Right? The ones that the pluses are the wild type. The ones without without then you would do a di hybrid cross. Because now you're looking at two different genes. Now I'm not going to fill this out but just know that you're not gonna get this recessive phenotype with a dye hybrid cross because all of the offspring will have a wild type of both genes. So they all appear wild type. Um So that's how that works. So let's look at example here so say you have three white mutants 12 and three and you want to know if the mutation causing them to be white is in the same gene for each mutant and the wild type color is normally blue. So this question is asking which mutations complement. And so what if you get the question like that? What does that mean? It says which mutations um compliment meaning that the two mutations from the two organisms are in different genes. So they complement. Not in the same genes are in different genes. So here you have your doing three crosses right? You're doing white one with white to white one with white three and white two with white three. And therefore that gets you all the mating possibilities that you can do with these three mutants. And you can see here that these all result in different things. Some of them are white and two of them are blue. So which mutations here complement? Meaning that the mutations are in different genes? Well let's go back up here to the rules and find out if the mutations are wild type which in this case is gonna be blue then the two mutations are in different genes. So here we have this one and here we have this one. So white one and three and white two and three compliment. And usually it's going to be you're gonna see white three because that's the that's the common factor. So white three compliments One and two most. How mostly how you're going to see that but F1 is all white if the mutation are all mutant which in this case and this problem is white. Then the two mutations are in the same gene. And so this is not a compliment because they're the same. These two are in different genes. So that's how you do a complementation test. You're definitely going to be asked about this. But just remember here if the offspring have the wild type phenotype there in different genes meaning that they complement if the offspring are all mutant, they're in the same gene means they don't. So with that let's now move on.

Okay, so now let's talk about non episodic jeans and these are going to be genes that their two genes typically two or more genes and they affect the same phenotype but they're not necessarily interacting and this is different from epistle which is the interaction of two genes. Now I'm presenting non episodic jeans first because this is gonna be what it's gonna be the closest to what you're familiar with and then we can base everything else, all the episodic genes in comparison to this. So let me back up here, first episode basis. And generally when this happens the presence of one gina leo will mask the phenotype of the second gene alil. So remember we're talking about non episodic here. So non episodic they won't mask it episodic, they will. And so in non episodic situations you're going to see the same ratio that you're used to seeing the 9 to 3 to 3 to 39 to 3 to 3 to one. In the epistle static you're going to see an altered ratio, it's going to be different and different types of episode Asus have different ratios that will go through all of these individually. But for now let's talk about this example, this is going to be focusing on corn snakes and corn snakes come in forward color patterns. You have orange black camouflage which is kind of a combination of orange and black and albino. Here's an example of a corn snake here, you can see that it has orange and black. So this would be a camouflaged coloration. There are two genes that control this O and B. Obviously O. Is for orange. B. Is for black. Now there are many different gina types you can have and you're going to see these charts a lot more coming up. So I want to explain it now. So here you can see that you have a dominant here and a line here. So what does the line means? The line means it can either be dominant or recessive. So here we have Homos I guess or hetero ziggy's dominant for oh and homos I guess recessive for B. So in this genotype you're going to get orange in the opposite meaning that this home is I guess recessive for oh and homo or hetero dominant for B. You're gonna get black. Now if you have a dominant allele for both the O. And the black or the B. You're going to get the camouflage, which is what this looks like, where you can see both the O. And the B. Or the orange and the black. And if you're recessive for both, you're going to get albino. So um we know this about the snakes. I'm giving this to you. So if we do a question like this, it says, what is the offspring's genotype and phenotype derived from the mating of two Hetero ziggy's camouflage corn snakes. So hetero ziggy's camouflage is going to be heterocyclic for both. O. And B. And because it's a mating, there's two of them so you can do a punnett square if you prefer. But I think that the branch method is going to be faster. You want to do a punnett square. Feel free to pause it right now. Right out your punnett square. Or even posit if you're gonna do the branch methods, see if you can figure out what the genotype sar um And the ratios for each and then come back and I'll do the explanation. So okay so hopefully you have positive and now you're restarting it and you're looking at the check your answers. So we're gonna walk through. So we're doing this hetero sickos mating with orange and black camouflaged here. So if we're gonna start with this our first is orange or not orange. So how do we do this? We do a basic punnett square. Oh so what you get is this so 3/4 will be orange and 1/4 will be not orange because the two recessive Os here the recessive little Os here can be a bunch of different colors. The albino can be black but just for right now we're saying not orange. Then for each we want to do the same for black. Now I can write out the punnett square but it's gonna look exactly like this. So I'm not going to actually do it. Um And it's gonna be the same for each. Then we can just do the math. Right? So 3/4 times 3/4 is 9/16. 3/4 times 1/4 is 3/16. And the saying here. 3/16 1 16th. So the quest And ask what are the offspring's genotype and phenotype? Well, nine out of 16 will be camouflaged, which means hetero Ziggy's for both. Three out of 16 will be orange. Three out of 16 will be black and one out of 16 will be albino. And so when we see this 9-3 to 3-1 ratio in a situation in which you know, two genes are working together to interact with the same phenotype. This is going to be non empty static. So this is the normal ratio that you're used to seeing. So this is the non episodic situation. So now let's move on and get to episodic situations.

Okay, so now we're gonna talk about episodic jeans. Now this is gonna be a long video. So you're gonna have to stick with me. And the reason is because I'm going over dominant episode basis and recessive episode basis which are different and have different um fanatic ratios at the end now. So just bear with me and I'm gonna give you some really great examples of both of these cases that you're gonna have to know because you're going to see them. Now. The important thing about this is with each type of episode basis and everything that I present from now on, I'm going to be giving you a ratio, it's not gonna be 9 to 3 to 3 to 39 to 3 to 3 to one, it's going to be something different and you're gonna have to know what ratio goes with what topic. So be sure that you're writing these ratios down because you will see these ratios in a test situation and you're gonna have to know which one goes with which. So the first thing that I'm talking about is dominant, episode Asus and this occurs when there's a dominant allele of one gene and it's masking the effect of a second gene. So remember episode basis is talking about two gene interaction. So there's two genes here, one of them is dominant and because that dominant allele is present, it's going to cover up or mask the phenotype of the other allele whether or not it's dominant or recessive. So we say here that the dominant allele is epic, static and the ratio of the fanatic ratio of across from a hetero sickos cross not 93 to 3 to one. But instead 12 to 3 to one memorize this and associated with this because 12 to 3 to one always means dominant episode basis. So I didn't mean to cover up the question. There we go. But um this is gonna be the example that I'm going to go. So let me back out here. So we're dealing with a certain breed of squash and it comes in three colors white, dark red and light red coloration is determined by two genes. D. And W. So here's an example of what this looks like. You have dominant D. And dominant. W. Remember that this line means it can be home as I guess dominant or hetero side. It doesn't matter just if there's at least one dominant allele. Then you get a white phenotype if you're excessive for the D. And dominant for the W. You also get a white phenotype. So this is this is different than what we've seen before. Now if you flip it and get a dominant D. And recess it ws you get dark red. And if you get recessive for both, you get light red. Now we say that the dominant W alil is episodic and the reason that we say this is because any time it's present that's the phenotype you're gonna get. So here the w. I'm gonna use a different color. So here the W. Is dominant. So you get white here the W. Is dominant. So you get white. The only time you will actually ever see this delisle is when the W dominant allele is not present. So this is an example of dominant episode Asus because the dominant W. Will always show no matter what the other one is. So um so that means that the dominant W. Is present, it will mask the phenotype of the deal. Now, how did we get to the 12 to 3 to one ratio? Well normally we see the 9 to 3 to 3 to 1 ratio right? Which is here and this is still the ratio for the genotype. So make sure you don't mix these up. The Jenna typical ratio over this is still 9 to 3 to 3 to 1. And if you don't believe me, you can totally do this on a punnett square or branch diagram. But if you want to trust me and believe me, this is this is it. This is your Jenna typical ratio. Now you're fanatic ratio is 12 to 3 to one because both of these are white. So you're going to see 12 white offspring, three dark red and one light red. Like I said, if you do not believe me, please go ahead, do this on a die hybrid punnett square or a branch diagram. Either way you're welcome to do it. But I guarantee you you're Jenna typical ratio will be 9 to 3 to 3 to 1, but you're fanatic ratio will be 12 to 3 to one. So if you get a question about any of these ratios, make sure you know whether or not it's talking about Jenna typical or fanatic. So that's dominant episode basis because the dominant W. Allele is episodic. But there's an alternate way and this is recessive episode episode basis. And this is when the recessive allele mask the phenotype of the second gene. And of course it has a different um ratio here 9 to 3 to four. Memorize this and know that it's associated with recessive episode basis, you're gonna have to know that. So let's go through an example. So this is with flour. So a certain breed of flour comes in three colors. Blue magenta and white coloration is determined by two genes. A wild type W. And a wild type. M. So notice this time we're talking about wild type versus mutant. Whereas before we were talking about dominant versus recessive either way it doesn't matter. But just know the notation notation is different. So if we have the wild type of deal for both the W and the M. You get a blue phenotype. If we have the wild type for the W. But mutant for the M. We get magenta. If you have the mutant version of the W. And the wild type for the M. You get white and if you have the mutant for both, you also get white. And so we say that the mutant W. Alil is episodic and it's recessive because it has to be present in two copies. Right? So any time that this is present it's going to be the same color, it's going to be white. So this means that when an organism has the two mutants, the recessive mutants it will mask the phenotype of any m combination. It will mask it when it's wild type and it will mask it when it's mutant. Doesn't matter this when it's present it will mask any other phenotype it could produce and it will produce white. Now the jena typical ratio for this remember Jenna typical genotype is still 9 to 3 to 3 to 1. Don't believe me do a punnett square. The fanatic ratio is 9 to 3 to four because both of these three plus one equals four are white. So be sure if you're given a question and you know it says well the ratio is 9-3-4. What is this representative of? You know this is recessive stasis. Now you might say, okay well this is great for a test. Um you know breeding flowers and probably not going to be doing this much in the future if you're going to be a geneticist. Great that's fantastic. But what is an example of this in real life. So there is an example of this in real life. And it's actually a recessive episode basis in humans. And we give it a special name called the Bombay phenotype because that's where it was first discovered. And this has to do with blood types. So let me walk through this slowly. So first there are two genes responsible for blood type, those in the eye family and those in the age family. Now, any time you've heard blood type before, you have only talked about these I jeans. Right? In terms of co dominance, we went over this before in the co dominance video. You have I. A. You have I. B. You can have I. A. I. B. Or little eyes. And these represent A B. A. B. And O. Now what what are we even talking about here? Right. So these are the jeans. And what do genes produce? They produce proteins. So if you have a blood that means you have the a protein on your blood cell. Which is fantastic. Right? That's how it's supposed to work. So what does the H family have to do with it? Well, in a normal blood cell, if you have this is your genotype then you're going to produce the A protein. So here's some a protein that's floating around now in order to get it onto the cell, the H protein has to come pick it up and then put it onto the cell. So if you don't have the H protein then you're not going to get any protein on the cell. this is not gonna work. And so what you're going to get is you're going to get a cell with nothing on it. And what does a cell with nothing on it resemble that's gonna be blood type O. Because it has no approaching on it. So what this looks like. So if you have any of the genotype with A. You're gonna produce blood type A. Because you produce protein A. The same with be the same with A. B. And if you have I you're not gonna you're not blood type O. Because you don't produce any protein. Now there is a rare mutation. Let me back up here. There is a rare mutation and we represent this using the little H. And the little H. If you have it you don't produce this protein. And therefore the it doesn't matter how much of this you produce. You can't ever add anything onto the blood cell. So we say that the H. H. Genotype is episodic sort of recessive episode basis because it masks the phenotype of any ill because it doesn't matter whether you're genotype is this this if you have the H. H. You can produce as much a protein as you want. But the H. Gene is not able to add that onto the blood cell. And so you look like you have blood type O. And it doesn't matter whether your genotype is for B. It's for I. A. I. B. Or O. If you have the recessive H. Is here your blood type is going to be, oh so if you get a question or something about, well how does A How how do two parents with type A. B. Blood produce offspring with O. Blood? The answer is recessive every stasis because you lack the protein that adds this onto the cell. So if you have a blood cell and your genotype is this and you're producing a ton of a protein and it's just sitting around, it's ready to go onto the cell. Then the h phenotype will add it and you'll get blood type A. The eight Little H. mutation cannot at it. And so you get blood type O. So recessive episode basis does actually exist in humans. It's not just if we're breeding these random colored flowers or squash or whatever this does actually exist. And if we did an actual cross with it the phenotype would be what 9-3-4 ratio. So this is real life stuff. It does actually have like a real life application. But for your situation you're gonna have to know dominant and recessive episode assis. You're gonna have to know the differences and it's super super super super super important that you know the fanatic ratios and the gina typical ratios and be able to tell those apart for each episode basis. So with that let's now move on

Okay so now let's talk about other types of gene interactions. So the first one I want to mention is the complementary gene action. And this is when two genes interact because they're in the same pathway. So you have a single pathway that includes you know six or seven or six or seven dozen genes that produce proteins that interact in this pathway. Well If you need one to start the other this is complimentary gene action. So the ratio here that you need to definitely know is 9-7. That's the super important one. So let's look an example here a breed of flour comes in two colors. Purple and white coloration is determined by two genes. Cmp. So here we have if you have a dominant C. And a dominant P. You're gonna get purple. If you have a dominant see but recessive P. You'll get white the same in the reverse with the recessive C. And the dominant P. White and recessive. Um For both you'll also get white. So you have to be dominant in both the sea and the P. In order to get this color. So the gina typical ratio will be 9 to 3 to 3 to 1. Don't believe me do a punnett square. But the fanatic ratio will be 9 to 7 because these ad 2 7 and they're all white. So that's how that works. So we say that these genes are complementary. They're working through complementary gene action because both gene needs to have a dominant allele in order to have that purple phenotype. So that's complimentary gene action. There's another type the second type called suppressors. And these are mutant allele. So now we're dealing with mutants that dominance mutants and the mutant of one gene will actually reverse the effects of a mutation and a second gene. So now we're working with two mutations. So there's two phenotype that you can get here the first and this is the most common. The one that I'm going to present to you and the one that you're most likely to be tested on is this and this is when the suppressor causes the phenotype to be like wild type and it'll have a 13-3 ratio the second. I'm not giving you an example of it does exist. A couple of your books mention it. Not all of you will even hear about it. But essentially it's different because the suppressor causes the phenotype to be mutant and it has a different ratio. Feel free just to throw that into your memory just in case you're asked about it. But most of the time if you're asked about a suppressor, it's gonna be the 13-3 case. So an example of this is a breed of flour comes in two colors. The wild type red and the mutant purple coloration is determined by two genes. P. And R. So um what we're dealing with here is if you have the wild type P. And the dominant are you get red if you have the wild type P. And the recessive are you also get red because the wild type P. Is making it red. If you have the recessive P. And the dominant are you get purple and the recessive in both. You get red. So in this case the wild type P leo and the dominant R. Liel both are causing the plant to be read. So the only time that you get it to be purple is the mutant P. L. E. L. And this is because the recessive suppressor which in this case is here is suppressing the purple phenotype. The press is the purple genotype. And so that's why it's red because normally these both would cause it to be purple. But because this is a suppressor it says no you're not gonna be purple. I'm repressing you and therefore I'm going to be read turns the plant bread. Now the jena typical ratio again is 9 to 3 to 3 to 1. However the fanatic ratio is going to be 13 To one because you have red red and red And our 13-3 sorry 13-3. And you have three purple. So there's where that ratio comes from. So that's super important for a suppressor. And then finally the very oh no where you have two more. So this is a little different though. These are modifiers and this is when a mutation in one gene changes the degree of expression. So kind of how much it's expressed of a mutated second gene. So here we go. So if you have wild type at both genes it's gonna be wild type. If you have wild type at one and mutant at another, it's going to be defective in some way. So an example of this is defective, it has low transcription. If you have mutant at one and wild type of the other, it's going to be also be defective but in a different way. So now you have this mutated protein A and it does something different that doesn't have anything to do with transcription but is a different pathway. And if your mutated in both their extremely defective. So this is a modifier because the mutation at one gene affects the degree of expression of a mutated second gene. So these are modifying each other and um causing the degree of expression to be defective or extremely defective. And these are sort of a rare case. Many of you may not even be asked about these but I wanted to throw it in there just in case that you were. And then finally synthetic lethal Z. And this is a lethal means dead of course. So this is when two viable single mutations result in death when found as a double. So I'm not even give you an example here but here's just to dominance are gonna be purple. One dominant will be cyan the other dominant will be white. But if you have um mutations in both its dead. So the Jenna typical ratio will be 9 to 3 to 3 to 1. But the fanatic pick will be 9 to 3 to three because this one you won't see because it's dead. So um this is a unique case to its, its, you may be asked about it, you may not but just in case I would memorize the ratios because that's how you're going to tell all of these different things apart. Um So if you see a 9 to 3 to three ratio, you know that this is because one of the alleles is a synthetic lethal, meaning that when you have double mutants. So when you have a mutated in this gene, the C. Gene and the P. Gene that causes it to be dead. So with that let's not move on.