Understanding Gene Interactions and Examples

Okay, so today everyone, so last meeting I have discussed with you a couple of gene interactions. And in our previous discussions, we have discussed novel phenotypes, we had your recessive epistasis, and then we had dominant epistasis. And I actually started discussing with you the first type of dominant epistasis. Now we will be dealing with dominant epistasis B, which is actually your second case. In dominant epistasis, I have presented with you the conditions. So we actually have CD or complete dominance in each gene pair. And with the complete dominance in each gene pair, when one gene is dominant, it's actually epistatic to the other. That's in your dominant epistasis B. But in your dominant epistasis A, when one gene is dominant, it is epistatic to the other. and when the other gene. So when the other gene is homorecessive, it is epistatic to the other. So now the expansion here from the initial dominant epistasis that we had is actually, we have two cases. So when one gene is dominant, it is affecting the other gene. And when the other gene is also homozygous recessive, it's also epistatic to the other gene. So this now probably indicates a combination. So if you're coming to think of it, so that you will remember, it's kind of like a combination of your recessive epistasis and your dominant epistasis A. And for this particular genetic interaction, the example that we classically use here is the feather color in fowl. So for the feather color in fowl, it's actually controlled by two genes. We have your gene I and then we have your gene C. So for your gene I, whenever you have a dominant allele, it actually results to color inhibition. So your color inhibition is considered to be dominant whereas your color expression is considered to be recessive. So for those fowls that are expressing colors, they're actually homozygous recessive. And for those fowls that are actually color inhibited, or I would say the color is white because there's no pigmentation, the genotype can be homozygous dominant, or it could be a heterozygous. So in the case of gene C, it actually results to kind of like a color is actually dominant. Color is dominant to non-color. So if the fowl is colored, therefore the genotype for the gene C is homozygous dominant or heterozygous whereas for non-color if there's no pigmentation then the genotype is actually homozygous recessive so now moving forward let's try to do the cross of a heterozygous for gene i and gene c for a rooster and a hand so we have a roaster here and then on this side we're are going to have your hand. And for your rooster, it's heterozygous. for I and then it's also heterozygous for C and then for your hen it's also heterozygous for I and in the same manner for your gene C it's also heterozygous. So now before we move forward to the planet square let's try to kind of like first identify the phenotype of the hen and the rooster that we have here. Let's first start with our rooster. So from our rooster, from the jinn eye. you can see that we have a dominant allele eye indicating that there's going to be color inhibition. So from here, we can say that there's a color inhibition from your gene I. And then we have your gene C. And your gene C says that there should be kind of like color. So now this is kind of like antagonizing each other. Your gene I is saying there's color inhibition. It should be white. But then your C is also dominant, and it's telling us right now that color should be expressed. But then going back to the conditions that I have provided with you, we have it here. In this type of dominant epistasis, when one gene is dominant, it is actually epistatic to the other gene. then that indicates that since your eye is actually dominant, then it is epistatic to your second gene. So therefore, even if your gene C is telling us that there should be color, but then your gene I is dominant and it's telling us that color should be inhibited, and this is a case of dominant epistasis, then the color of our rooster is actually white, and then the color of our hen having the same genotype is also going to be white. So moving on with this, I'm going to give you time on your own. to kind of like identify the gametes and develop your own planet square. So then again, whenever we solve problems, I always tell you I want the male gametes to be on top and then on the side, I would like to see the female gametes. So I'm giving you five minutes to kind of like do things on your own, identify the gametes and do the crosses. You can kind of like decide to follow me on what I'm going to do, or you could also decide to do it on your own seats or on your own notes. So you can kind of like figure out if you are following with the lecture or not. So I'm giving you five minutes to work on this. oh let me do it on my own so we'll have here a dominant dominant a dominant with recessive a recessive with dominant and the recessive with recessive in here it's the same gametes that you get because you know we are all dealing with uh the same genotype for the parents a dominant I dominant C, a dominant I recessive C, then we're gonna have here a recessive I dominant C, and then we'll have here a recessive I recessive C. So if we're going to do this, we have a dominant I dominant I dominant C dominant C, dominant I dominant I dominant C recessive C, a dominant I recessive I, dominant C dominant C. a dominant i recessive i dominant c recessive c a dominant i dominant i dominant c recessive c both dominant i both recessive c uh dominant i recessive i don't mean c recessive c a dominant i recessive i recessive c recessive c a dominant i recessive i dominant c dominant c dominant I excessive I don't mean the recessive C and then a recessive I recessive I dominant C dominant C and then let me just kind of like change the the thickness okay let's see if this works better and then we'll have here a recessive I recessive I dominant C recessive C and then dominant I recessive I dominant C recessive C dominant I recessive I recessive C dominant I, dominant I, dominant C, recessive C, and then it's homozygous recessive for I, and then it's homozygous recessive for C. So I just want to point out that we are in dominant epistasis B, and we are talking about, so this is the letter D, we are talking about gene. interactions. So now moving forward with this one, let's now try to identify the phenotypes that we can have. So again, in identifying phenotype genotypes, I have told you that it would be best to summarize it kind of like putting together the four general genotypes that you can have so that it's easier for you to count the phenotypes. Of course, the phenotypic ratio here, the phenotypic, I'm sorry again, our genotypic ratio is actually, it's the same. It's 1 is to 2 is to 1 is to 2 is to 4 is to 2 is to 1 is to 2 is to 1. So it's all the same because it's a dihybrid cross. But let's try to summarize the genotypes into kind of like four general categories. Again, I have a dominant eye, regardless of the second allele. And then for my gene C, I have a dominant C regardless of the second allele. And then I'm going to have my dominant eye again. And then the second allele could be dominant or recessive. And then my C is homozygous recessive. And then I'm going to my homozygous recessive eye. And then I'll have a copy of my dominant C regardless of... the second allele for gene C, and then I have homozygous recessive I, and then I have homozygous recessive C. So before we move forward, let's try to kind of like look at them. Like if you're going to look at your, if you're going to look at again your, your Punnett square for this kind of genotype, I actually have nine. So that's going to be one, two, three, four, five, six, seven, eight, nine. So I will have nine of this. And then for the second genotype, general genotype, I actually have three. So that's going to be this one. That's one, two. And then that's going to be the third. And then for the third general genotype, I actually have three again. Let's kind of mark them in rectangle. So that's going to be one. This will be two. And this will be. the third one. So next is the last. So for this one, we only have one. So that's going to be this. Now let's try to identify the phenotypes. So for the first one, I have my gene I. So if we go back here again, if you have a copy of your dominant I, if you have a copy of your dominant I, it's actually epistatic to the first. So therefore, epistatic to the other gene. So therefore, even if I have gene C telling me that there should be color inhibition, this actually affects that. So therefore, the color of this one is actually white. And then let's move forward to the second one. So the second one, I have a copy of my dominant eye again, and it's dominantly epistatic to the second gene. So therefore, the color of this one is white. And then moving forward, I have here a recessive I, recessive I. It's telling me that there should be color expression this time. So therefore, there's no inhibition here. But then you move to the second gene, which is telling you that there should be color. So both gene I and gene C are telling you that there should be color. So this file. is going to be colored. And then for the last one, you take a look at this example. It's telling you... that the fowl should be carrying the genotype for color inhibition. It's telling you that it should be. No, there's no color inhibition here. So it's homozygous recessive eye. So when you have a homozygous recessive eye, then it indicates that there should be color expression because the dominant eye is for color inhibition. So in here, it's telling you that there should be expression. But then again, one of the conditions in our dominant epistasis, if you go back here, if you go back in dominant epistasis, it says that when the other gene is homozygous recessive, it is actually epistatic to the other. So if you go here, even if it's telling you that there should be color expression, then since your second gene is actually homozygous recessive, Now it is starting to be epistatic to the first gene. So therefore, the color of this one, since we should not have color expression, then the color of individuals having this genotype is actually white. So therefore, looking at this one, our phenotypic ratio for dominant epistasis B would actually be... Can you do the counting for me? So that's going to be 9. That's going to be giving you a phenotypic ratio of 15 is to 1. So indicating that I'm sorry, it's not 15 is to 1. My bad. So this is not right. The phenotypic ratio is actually going to be, I'd say, 13 is to 3. So 13. will actually be white so the 13 will actually be white and then for your tree this is gonna be your uh colored just uh give me a second i just have to Just a reference real quick. Yeah, I'm back. Let's continue with the lecture. Now we are done with your dominant epistasis B. So we are moving forward with another type of genetic interaction, which we call your complementary gene action or complementary genes. Complementary. genes or we call it your complementary gene action. So let's take a look at the conditions first. So in your complementary gene action, there is complete dominance in each gene pair. So there's complete dominance in each gene pair. Either recessive homozygous is epistatic to the other gene. So now this is kind of like, don't get confused with the recessive epistasis. In recessive epistasis, we have a major gene and then only one gene is. when homozygous recessive is epistatic to the other. Now in this situation, we are still talking of two genes, but then what happens now is that when one gene, the first gene is homozygous recessive, it's epistatic to the second. And in the same manner, when your second gene is also homozygous recessive, it's epistatic to the first. homozygous recessive in the first is affecting the second and homozygous recessive in the second like is also affecting your your first so for the example that we will be having for this type of gene interaction we are actually going into the flower color the flower color in pea plants in pea for the flower Boop. color in P, we actually have two genes that are influencing it. We actually have your gene P and your gene C. And I would like to emphasize here that for pigment production, for pigment production, dominant allele for both genes Peace. is required. So in order for the pigment to be produced, so what I mean here, you need a dominant copy of your gene P and you also need, so this is a requirement for pigmentation, you also need a dominant copy of your allele C, at least one dominant because we have complete dominance in both gene pairs. So in this example that we will be having, we are talking about two genes, your P is actually coding for the color purple and it is dominant to the color white. So for white, it's going to be homozygous recessive P and for it to be purple, you can have two genotypes here. It can be homozygous dominant P or it can be heterozygous P. So now let's go to the second gene. So your second gene is C, regardless again of the second allele. And if you have a copy of your dominant C, you're going to have color expression. And your color expression is actually dominant to non-color expression. So therefore, for no color expression, The genotype is homozygous recessive C. And for color expression, we can have two genotypes for gene C. It can be homozygous dominant C or it can be heterozygous C. So now let's move forward and let's do the cross again from this one. So if you're going to do this, again, I'm giving you a couple of minutes to work on your own in your seats while I'm doing my own stuff here. you can use your notes and then you can identify the gametes and do the the cross like the planet square because you know if you get to master this one exams will be kind of like easy for you so the parents that we are using here in this cross it's the same it's heterozygous for p and heterozygous for c this is gonna be your male and then for the female it's also heterozygous for p and it's also So heterozygous. for C. So before we do the dihybrid cross and before identifying the gametes, let us first identify the color of these parents that we are dealing with. So we are here having in your gene P here, we have a dominant P. And if you look at the condition here, a dominant P is actually dominant to your recessive P and your dominant P codes for the color purple. So therefore, This is gonna be purple. It's telling us that it's purple. And now let's take a look at your gene C. In your gene C, you look at the condition again. Your color expression is dominant to non-color expression. And in here, we have a dominant C. So therefore, there's gonna be color expression. So from dealing with the two genes, we can say therefore that the color of the flower from the male parent is going to be purple and then since it has the same genotype as the female as the female parent has the same genotype as the male parent and therefore the color of this one is also purple. Now I'm gonna shut mine out and now you can move forward on identifying the gametes from the parental genotypes that I have provided with you and I'm gonna do it on my own. You can check it afterwards after I finish my planet square. Okay, I'm done. And now you can counter check your own work. Now we are doing the same drill again, just as what we did with the other types of gene interactions. So our genotypic ratio, the classical 1, 2, 1, 2, 4, 2, 1, 2, 1. Well, basically, you know this now by heart. So let's try to identify our general. genotypes from this cross. Of course, we know that you will have 9, 3, 3, and then 1 again. So in here, we have a dominant P regardless of the second, and then we have a copy of your dominant C. Here we have a dominant P, and then your C is homozygous recessive. And then here we have a homozygous recessive P and at least one copy of your dominant C. And then lastly, we have here homozygous recessive P and homozygous recessive C. So now for these genotypes that we are having now, let's try to identify their corresponding phenotypes. So if we go back to the condition again, now this will be very easy class because in the complementary gene action. So what is required again for the first gene, we need to at least have one dominant allele. And then for the second gene, we also have to have at least one dominant allele. So we want one copy of your dominant P and one copy, at least one copy of your dominant P and at least one copy of your recessive C such that there is pigmentation. And from that pigmentation, we will be getting the color or the phenotype purple. So from that, you can immediately tell that for the first general genotype that we had, we have a copy of your dominant P, and then we are going to be having the color purple. And then for the second genotype, I have a copy of my dominant P, but then my C is homozygous recessive. So again, just to refresh you, I just had mentioned a while ago that for color to be expressed, we have to at least have one dominant P and one dominant C. So therefore, since here we don't have a copy of your dominant C, the color is actually going to be white. And then for this one, we have dominant C, but then your P is devoid of a dominant allele P. So therefore, the color is also white. And lastly, this one, obviously, the color of the flower is also going to be white. So if you're going to... Take a look at the total. This is 7. And for purple, we have actually 9. So therefore, our phenotypic ratio from complementary gene action is actually 9 is to 7. And one thing I would like to emphasize here is the type of interaction that we are getting. So the interaction. So what is the interaction that we are getting here? So it means here that the genes P and C produces enzymes. So they produce enzymes that actually catalyze. They actually catalyze successive steps in a biochemical process leading to production of pigments. To production of pigments. And when I say that, I mean, let's... try to kind of like illustrate it in a way that it's easy for you to kind of like understand. So we have here gene P and then here we have your gene C. So your gene P actually produces an enzyme which we will call here hypothetically as your enzyme P and your gene C actually codes for an enzyme which we will call here as your enzyme C. And then in this process, we have here a precursor. When we say it's a precursor, it's a compound that is actually necessary for you to be able to produce a product in a biochemical reaction. And this enzyme P actually catalyzes a pathway that converts this precursor into a product which is actually required to produce the pigment. Still, the color here is white because the product is not yet a pigment, but then this white product here is actually essential for you to be able to produce the pigment, which we are seeing phenotypically actually as purple. So again, in complementary gene action, whenever you see a complementary gene action, it means that the two genes that you are dealing with are actually kind of like catalyzing. two successive steps. And when you are actually mutated in one of them, or when you are homozygous recessive in one of them, then there's no way that you are producing the final output in which in this example that we are talking about, it's a pigment that actually results in a phenotypic color, which is purple. Because imagine if you have recessive C here, if you're going to omit this, and it's homozygous recessive C, then the color will be white. and even this one is homozygous dominant, but this one is homozygous recessive P, then you're not going to be able to pass this pathway. Your precursor stays as a precursor, and there's not going to be production of the pigment, which is showing phenotypically as your purple. So that's the fifth type of gene interaction, I guess. So now we are moving forward to ABT. We are moving forward to the sixth type of gene interaction. So we are in your letter F right now, the sixth type of gene interaction, which is your duplicate gene action. Or we call it as your duplicate. Let me just write it. Sometimes it is called as your duplicate genes. So again, And... Let's first deal with the conditions. We have complete dominance in each gene pair, but either gene when dominant is epistatic to the other. So, but either gene when dominant is epistatic to the other. So, to simplify this one. From the word duplicate, we have two genes that are doing the same thing. So again, for you to remember this from the word duplicate, to simplify it, it just means that, well, we have the case here that I have provided. But for you to be able to remember it immediately when we say duplicate genes, oh, it's a copy. So I have two copies. I have a duplicate of it. So I have gene A doing the same thing. And whatever my gene A is doing, it's also done by my gene B. Okay, so an example that we have here is actually... your uh so the example that we will be using here is your let me just kind of like make this heavier so our example here is the seed capsule in shepherd's purse i don't know what the shepherd's purse is It's a seed capsule, so we are probably talking about a plant. So you can figure it out. You can Google it. I'm not going to do it for you. You can just search for it and see how it looks like. And they are actually saying that in shepherd's purse, for the shape of the seed capsule, let's just add here shape of seed capsule. So the shape of the seed capsule in shepherd's purse, there's actually two genes that are involved. We have your gene A, and then we have your... gene B. So for your gene A, the triangular is dominant to the ovoid shape. And then since it's a duplicate gene action, therefore, for your second gene, which is your gene B, your triangular is also dominant to your ovoid. Now you realize why when you have a dominant allelin one, it's epistatic to the second because they're because they do the same thing. So therefore, for an ovoid, it should be homozygous recessive for A, and for B, it should also be homozygous recessive. So for triangular, you can have a homozygous dominant for A and a heterozygous for A. And for your gene B, you can have a homozygous dominant B and a heterozygous for B. So now let's do the dihybrid cross again. We have heterozygous for A and heterozygous for B. This is your male parent. And then for your female parent, that's going to be heterozygous for A and then heterozygous for B. Again, same drill. Getting tired of this. Let's try to identify the phenotypes. So this tells triangular and this tells triangular. So therefore, the shape of the seed capsule for... Your male parent is triangular and then for your female parent, it's also triangular. So let's continue. I'm going to shut my mouth again. And then you can move forward on identifying the gametes and then do the crosses in your own panet square. But then I would like to repeat the top gamete should just always be the male and then the side gamete should be your... female so let me do this on my own uh and do it also in your own notes and we'll check later and my bad that's wrong comment a recessive b recessive a dominant b i'm getting tired of this So okay we're done. Now let's do the genotypic ratio again. This is getting it's 1, 2, 1, 2, 4, 2, 1, 2, 1. Now let's try to identify the general genotypes that we can get from this cross. We have the 9 of course a dominant A regardless of the second and a dominant B regardless of the second allele. We have 3 dominant A. And then homozygous recessive for B. We have a homozygous recessive A. And then at least one copy of your dominant B. And then one homo recessive A. And then we have homo recessive B. Where are they coming from? Again, look at the Punnett square. The 9 is coming from this. That's going to be your 9. Your tree is actually coming from the encircled genotypes. The other tree is actually coming from the squared or rectangular genotypes. And the one is actually coming from the crossed out genotype. So let's try to identify the phenotypes of these general genotypes that we have. So here we have a dominant A, dominant B. A saying triangular, B saying triangular. So this is going to be triangular. And then this one, it's going to be triangular. This one is also triangular. But then this one is going to be ovoid. So in duplicate gene action, what is the phenotypic ratio that we are getting from this cross? So if we do a heterozygous for both gene pairs, for the male parent and the female parent, the phenotypic ratio that we are getting in duplicate gene action is actually 50. is to 1. I hope you were able to get that. I think before we move forward to the next lecture, let's kind of like try to summarize what we have discussed for the last two lectures. So we actually discussed your gene. I don't know why it became... Okay, so we discussed about gene. interactions. So let me make it thicker. So we had gene interactions and in your gene interactions we have case number one, the first type of gene interaction, we have your novel phenotype. So that you will remember this for novel phenotype, what is the example that we used? The example that we use here is the comb type in chicken. So for the comb type of chicken, we actually had four phenotypes. We have your rose, we have your pea, we have your walnut, and then lastly, we had your single comb. But then what is our phenotypic ratio? Our phenotypic ratio in this type of gene interaction is actually 9 is to 3 is to 3. is to one. So hold on, nine is to three is to three is to one. The next, let's move to the second type of gene interaction. We discuss your recessive epistasis. So in your recessive epistasis, the example that we had in here is actually the coat color in mice. So it's in your mouse. coat color and in your mouse coat color we actually had three we had your agouti which is dominant over your black but then we have a recessive allele which is actually causing albinism which is your white so therefore there are three colors that we can get so there are three coat colors we have your agouti we have your black and then lastly we have your albino So in here, our phenotypic ratio from this type of genetic interaction is actually 9 is to 3 is to 4. So after we finish recessive epistasis, we discuss your dominant epistasis. But your dominant epistasis are actually divided into two cases. We have your dominant epistasis A. And in your dominant epistasis A, the example that we use here is actually your fruit color in summer squash. So for the fruit color in summer squash, we actually had your white and then we have your yellow and then we also had your green. green. And then our phenotypic ratio in this type of genetic interaction is actually 12 is to 3 is to 1. After that, we proceeded to go into your dominant epistasis B. And our example for your dominant epistasis B is the feather color in fowl. So for the feather color in fowl, we divided it into two phenotypes. They can be white or they can be colored. And then our phenotypic ratio that we... Actually, head in here is actually 13 is to 3, wherein we have more white and then a few colored, which is actually 3. After dominant epistasis, we just finish covering from this session your complementary gene action or complementary genes. And for the complementary genes, The example that we had is actually your flower color in P. And for the flower color in P, how many phenotypes did we have? We actually had two phenotypes. It can be purple, and then it can also be white or non-colored. So for the phenotypic ratio in this type of genetic interaction, it was actually... 9 is to 7. So these are the signatures for the different genetic interactions, the phenotypic ratios. And then lastly, we just finished covering your duplicate gene action or your duplicate genes. And our example for this type of genetic interaction is actually your shape of of seed capsule in shepherd's purse and it's very long seed capsule in shepherd's purse we have two phenotypes here the seed capsule can be triangular or it can be ovoid and the phenotypic ratio is actually 15 is to 1 so i think for the lecture on gene interactions. I'm gonna wrap it up here. Now we are moving forward to another lecture which is on pseudoalleles and I will be discussing that in a different session. So you all have a great day.

In dominant epistasis, I have presented with you the conditions. So we actually have CD or complete dominance in each gene pair. And with the complete dominance in each gene pair, when one gene is dominant, it's actually epistatic to the other.

That's in your dominant epistasis B. But in your dominant epistasis A, when one gene is dominant, it is epistatic to the other. and when the other gene.

So when the other gene is homorecessive, it is epistatic to the other. So now the expansion here from the initial dominant epistasis that we had is actually, we have two cases. So when one gene is dominant, it is affecting the other gene. And when the other gene is also homozygous recessive, it's also epistatic to the other gene. So this now probably indicates a combination.

So if you're coming to think of it, so that you will remember, it's kind of like a combination of your recessive epistasis and your dominant epistasis A. And for this particular genetic interaction, the example that we classically use here is the feather color in fowl. So for the feather color in fowl, it's actually controlled by two genes.

We have your gene I and then we have your gene C. So for your gene I, whenever you have a dominant allele, it actually results to color inhibition. So your color inhibition is considered to be dominant whereas your color expression is considered to be recessive.

So for those fowls that are expressing colors, they're actually homozygous recessive. And for those fowls that are actually color inhibited, or I would say the color is white because there's no pigmentation, the genotype can be homozygous dominant, or it could be a heterozygous. So in the case of gene C, it actually results to kind of like a color is actually dominant. Color is dominant to non-color. So if the fowl is colored, therefore the genotype for the gene C is homozygous dominant or heterozygous whereas for non-color if there's no pigmentation then the genotype is actually homozygous recessive so now moving forward let's try to do the cross of a heterozygous for gene i and gene c for a rooster and a hand so we have a roaster here and then on this side we're are going to have your hand.

And for your rooster, it's heterozygous. for I and then it's also heterozygous for C and then for your hen it's also heterozygous for I and in the same manner for your gene C it's also heterozygous. So now before we move forward to the planet square let's try to kind of like first identify the phenotype of the hen and the rooster that we have here.

Let's first start with our rooster. So from our rooster, from the jinn eye. you can see that we have a dominant allele eye indicating that there's going to be color inhibition. So from here, we can say that there's a color inhibition from your gene I.

And then we have your gene C. And your gene C says that there should be kind of like color. So now this is kind of like antagonizing each other. Your gene I is saying there's color inhibition. It should be white.

But then your C is also dominant, and it's telling us right now that color should be expressed. But then going back to the conditions that I have provided with you, we have it here. In this type of dominant epistasis, when one gene is dominant, it is actually epistatic to the other gene. then that indicates that since your eye is actually dominant, then it is epistatic to your second gene.

So therefore, even if your gene C is telling us that there should be color, but then your gene I is dominant and it's telling us that color should be inhibited, and this is a case of dominant epistasis, then the color of our rooster is actually white, and then the color of our hen having the same genotype is also going to be white. So moving on with this, I'm going to give you time on your own. to kind of like identify the gametes and develop your own planet square.

So then again, whenever we solve problems, I always tell you I want the male gametes to be on top and then on the side, I would like to see the female gametes. So I'm giving you five minutes to kind of like do things on your own, identify the gametes and do the crosses. You can kind of like decide to follow me on what I'm going to do, or you could also decide to do it on your own seats or on your own notes.

So you can kind of like figure out if you are following with the lecture or not. So I'm giving you five minutes to work on this. oh let me do it on my own so we'll have here a dominant dominant a dominant with recessive a recessive with dominant and the recessive with recessive in here it's the same gametes that you get because you know we are all dealing with uh the same genotype for the parents a dominant I dominant C, a dominant I recessive C, then we're gonna have here a recessive I dominant C, and then we'll have here a recessive I recessive C. So if we're going to do this, we have a dominant I dominant I dominant C dominant C, dominant I dominant I dominant C recessive C, a dominant I recessive I, dominant C dominant C.

a dominant i recessive i dominant c recessive c a dominant i dominant i dominant c recessive c both dominant i both recessive c uh dominant i recessive i don't mean c recessive c a dominant i recessive i recessive c recessive c a dominant i recessive i dominant c dominant c dominant I excessive I don't mean the recessive C and then a recessive I recessive I dominant C dominant C and then let me just kind of like change the the thickness okay let's see if this works better and then we'll have here a recessive I recessive I dominant C recessive C and then dominant I recessive I dominant C recessive C dominant I recessive I recessive C dominant I, dominant I, dominant C, recessive C, and then it's homozygous recessive for I, and then it's homozygous recessive for C. So I just want to point out that we are in dominant epistasis B, and we are talking about, so this is the letter D, we are talking about gene. interactions.

So now moving forward with this one, let's now try to identify the phenotypes that we can have. So again, in identifying phenotype genotypes, I have told you that it would be best to summarize it kind of like putting together the four general genotypes that you can have so that it's easier for you to count the phenotypes. Of course, the phenotypic ratio here, the phenotypic, I'm sorry again, our genotypic ratio is actually, it's the same. It's 1 is to 2 is to 1 is to 2 is to 4 is to 2 is to 1 is to 2 is to 1. So it's all the same because it's a dihybrid cross. But let's try to summarize the genotypes into kind of like four general categories.

Again, I have a dominant eye, regardless of the second allele. And then for my gene C, I have a dominant C regardless of the second allele. And then I'm going to have my dominant eye again.

And then the second allele could be dominant or recessive. And then my C is homozygous recessive. And then I'm going to my homozygous recessive eye.

And then I'll have a copy of my dominant C regardless of... the second allele for gene C, and then I have homozygous recessive I, and then I have homozygous recessive C. So before we move forward, let's try to kind of like look at them.

Like if you're going to look at your, if you're going to look at again your, your Punnett square for this kind of genotype, I actually have nine. So that's going to be one, two, three, four, five, six, seven, eight, nine. So I will have nine of this.

And then for the second genotype, general genotype, I actually have three. So that's going to be this one. That's one, two. And then that's going to be the third. And then for the third general genotype, I actually have three again.

Let's kind of mark them in rectangle. So that's going to be one. This will be two.

And this will be. the third one. So next is the last. So for this one, we only have one. So that's going to be this.

Now let's try to identify the phenotypes. So for the first one, I have my gene I. So if we go back here again, if you have a copy of your dominant I, if you have a copy of your dominant I, it's actually epistatic to the first. So therefore, epistatic to the other gene. So therefore, even if I have gene C telling me that there should be color inhibition, this actually affects that.

So therefore, the color of this one is actually white. And then let's move forward to the second one. So the second one, I have a copy of my dominant eye again, and it's dominantly epistatic to the second gene. So therefore, the color of this one is white. And then moving forward, I have here a recessive I, recessive I.

It's telling me that there should be color expression this time. So therefore, there's no inhibition here. But then you move to the second gene, which is telling you that there should be color.

So both gene I and gene C are telling you that there should be color. So this file. is going to be colored. And then for the last one, you take a look at this example. It's telling you...

that the fowl should be carrying the genotype for color inhibition. It's telling you that it should be. No, there's no color inhibition here.

So it's homozygous recessive eye. So when you have a homozygous recessive eye, then it indicates that there should be color expression because the dominant eye is for color inhibition. So in here, it's telling you that there should be expression.

But then again, one of the conditions in our dominant epistasis, if you go back here, if you go back in dominant epistasis, it says that when the other gene is homozygous recessive, it is actually epistatic to the other. So if you go here, even if it's telling you that there should be color expression, then since your second gene is actually homozygous recessive, Now it is starting to be epistatic to the first gene. So therefore, the color of this one, since we should not have color expression, then the color of individuals having this genotype is actually white.

So therefore, looking at this one, our phenotypic ratio for dominant epistasis B would actually be... Can you do the counting for me? So that's going to be 9. That's going to be giving you a phenotypic ratio of 15 is to 1. So indicating that I'm sorry, it's not 15 is to 1. My bad.

So this is not right. The phenotypic ratio is actually going to be, I'd say, 13 is to 3. So 13. will actually be white so the 13 will actually be white and then for your tree this is gonna be your uh colored just uh give me a second i just have to Just a reference real quick. Yeah, I'm back. Let's continue with the lecture. Now we are done with your dominant epistasis B.

So we are moving forward with another type of genetic interaction, which we call your complementary gene action or complementary genes. Complementary. genes or we call it your complementary gene action.

So let's take a look at the conditions first. So in your complementary gene action, there is complete dominance in each gene pair. So there's complete dominance in each gene pair. Either recessive homozygous is epistatic to the other gene. So now this is kind of like, don't get confused with the recessive epistasis.

In recessive epistasis, we have a major gene and then only one gene is. when homozygous recessive is epistatic to the other. Now in this situation, we are still talking of two genes, but then what happens now is that when one gene, the first gene is homozygous recessive, it's epistatic to the second. And in the same manner, when your second gene is also homozygous recessive, it's epistatic to the first. homozygous recessive in the first is affecting the second and homozygous recessive in the second like is also affecting your your first so for the example that we will be having for this type of gene interaction we are actually going into the flower color the flower color in pea plants in pea for the flower Boop. color in P, we actually have two genes that are influencing it.

We actually have your gene P and your gene C. And I would like to emphasize here that for pigment production, for pigment production, dominant allele for both genes Peace. is required.

So in order for the pigment to be produced, so what I mean here, you need a dominant copy of your gene P and you also need, so this is a requirement for pigmentation, you also need a dominant copy of your allele C, at least one dominant because we have complete dominance in both gene pairs. So in this example that we will be having, we are talking about two genes, your P is actually coding for the color purple and it is dominant to the color white. So for white, it's going to be homozygous recessive P and for it to be purple, you can have two genotypes here.

It can be homozygous dominant P or it can be heterozygous P. So now let's go to the second gene. So your second gene is C, regardless again of the second allele.

And if you have a copy of your dominant C, you're going to have color expression. And your color expression is actually dominant to non-color expression. So therefore, for no color expression, The genotype is homozygous recessive C.

And for color expression, we can have two genotypes for gene C. It can be homozygous dominant C or it can be heterozygous C. So now let's move forward and let's do the cross again from this one.

So if you're going to do this, again, I'm giving you a couple of minutes to work on your own in your seats while I'm doing my own stuff here. you can use your notes and then you can identify the gametes and do the the cross like the planet square because you know if you get to master this one exams will be kind of like easy for you so the parents that we are using here in this cross it's the same it's heterozygous for p and heterozygous for c this is gonna be your male and then for the female it's also heterozygous for p and it's also So heterozygous. for C. So before we do the dihybrid cross and before identifying the gametes, let us first identify the color of these parents that we are dealing with. So we are here having in your gene P here, we have a dominant P.

And if you look at the condition here, a dominant P is actually dominant to your recessive P and your dominant P codes for the color purple. So therefore, This is gonna be purple. It's telling us that it's purple.

And now let's take a look at your gene C. In your gene C, you look at the condition again. Your color expression is dominant to non-color expression. And in here, we have a dominant C.

So therefore, there's gonna be color expression. So from dealing with the two genes, we can say therefore that the color of the flower from the male parent is going to be purple and then since it has the same genotype as the female as the female parent has the same genotype as the male parent and therefore the color of this one is also purple. Now I'm gonna shut mine out and now you can move forward on identifying the gametes from the parental genotypes that I have provided with you and I'm gonna do it on my own. You can check it afterwards after I finish my planet square. Okay, I'm done.

And now you can counter check your own work. Now we are doing the same drill again, just as what we did with the other types of gene interactions. So our genotypic ratio, the classical 1, 2, 1, 2, 4, 2, 1, 2, 1. Well, basically, you know this now by heart.

So let's try to identify our general. genotypes from this cross. Of course, we know that you will have 9, 3, 3, and then 1 again. So in here, we have a dominant P regardless of the second, and then we have a copy of your dominant C. Here we have a dominant P, and then your C is homozygous recessive.

And then here we have a homozygous recessive P and at least one copy of your dominant C. And then lastly, we have here homozygous recessive P and homozygous recessive C. So now for these genotypes that we are having now, let's try to identify their corresponding phenotypes.

So if we go back to the condition again, now this will be very easy class because in the complementary gene action. So what is required again for the first gene, we need to at least have one dominant allele. And then for the second gene, we also have to have at least one dominant allele. So we want one copy of your dominant P and one copy, at least one copy of your dominant P and at least one copy of your recessive C such that there is pigmentation. And from that pigmentation, we will be getting the color or the phenotype purple.

So from that, you can immediately tell that for the first general genotype that we had, we have a copy of your dominant P, and then we are going to be having the color purple. And then for the second genotype, I have a copy of my dominant P, but then my C is homozygous recessive. So again, just to refresh you, I just had mentioned a while ago that for color to be expressed, we have to at least have one dominant P and one dominant C.

So therefore, since here we don't have a copy of your dominant C, the color is actually going to be white. And then for this one, we have dominant C, but then your P is devoid of a dominant allele P. So therefore, the color is also white.

And lastly, this one, obviously, the color of the flower is also going to be white. So if you're going to... Take a look at the total. This is 7. And for purple, we have actually 9. So therefore, our phenotypic ratio from complementary gene action is actually 9 is to 7. And one thing I would like to emphasize here is the type of interaction that we are getting.

So the interaction. So what is the interaction that we are getting here? So it means here that the genes P and C produces enzymes.

So they produce enzymes that actually catalyze. They actually catalyze successive steps in a biochemical process leading to production of pigments. To production of pigments.

And when I say that, I mean, let's... try to kind of like illustrate it in a way that it's easy for you to kind of like understand. So we have here gene P and then here we have your gene C.

So your gene P actually produces an enzyme which we will call here hypothetically as your enzyme P and your gene C actually codes for an enzyme which we will call here as your enzyme C. And then in this process, we have here a precursor. When we say it's a precursor, it's a compound that is actually necessary for you to be able to produce a product in a biochemical reaction. And this enzyme P actually catalyzes a pathway that converts this precursor into a product which is actually required to produce the pigment.

Still, the color here is white because the product is not yet a pigment, but then this white product here is actually essential for you to be able to produce the pigment, which we are seeing phenotypically actually as purple. So again, in complementary gene action, whenever you see a complementary gene action, it means that the two genes that you are dealing with are actually kind of like catalyzing. two successive steps.

And when you are actually mutated in one of them, or when you are homozygous recessive in one of them, then there's no way that you are producing the final output in which in this example that we are talking about, it's a pigment that actually results in a phenotypic color, which is purple. Because imagine if you have recessive C here, if you're going to omit this, and it's homozygous recessive C, then the color will be white. and even this one is homozygous dominant, but this one is homozygous recessive P, then you're not going to be able to pass this pathway. Your precursor stays as a precursor, and there's not going to be production of the pigment, which is showing phenotypically as your purple.

So that's the fifth type of gene interaction, I guess. So now we are moving forward to ABT. We are moving forward to the sixth type of gene interaction.

So we are in your letter F right now, the sixth type of gene interaction, which is your duplicate gene action. Or we call it as your duplicate. Let me just write it. Sometimes it is called as your duplicate genes.

So again, And... Let's first deal with the conditions. We have complete dominance in each gene pair, but either gene when dominant is epistatic to the other. So, but either gene when dominant is epistatic to the other.

So, to simplify this one. From the word duplicate, we have two genes that are doing the same thing. So again, for you to remember this from the word duplicate, to simplify it, it just means that, well, we have the case here that I have provided. But for you to be able to remember it immediately when we say duplicate genes, oh, it's a copy.

So I have two copies. I have a duplicate of it. So I have gene A doing the same thing. And whatever my gene A is doing, it's also done by my gene B.

Okay, so an example that we have here is actually... your uh so the example that we will be using here is your let me just kind of like make this heavier so our example here is the seed capsule in shepherd's purse i don't know what the shepherd's purse is It's a seed capsule, so we are probably talking about a plant. So you can figure it out. You can Google it. I'm not going to do it for you.

You can just search for it and see how it looks like. And they are actually saying that in shepherd's purse, for the shape of the seed capsule, let's just add here shape of seed capsule. So the shape of the seed capsule in shepherd's purse, there's actually two genes that are involved.

We have your gene A, and then we have your... gene B. So for your gene A, the triangular is dominant to the ovoid shape.

And then since it's a duplicate gene action, therefore, for your second gene, which is your gene B, your triangular is also dominant to your ovoid. Now you realize why when you have a dominant allelin one, it's epistatic to the second because they're because they do the same thing. So therefore, for an ovoid, it should be homozygous recessive for A, and for B, it should also be homozygous recessive. So for triangular, you can have a homozygous dominant for A and a heterozygous for A. And for your gene B, you can have a homozygous dominant B and a heterozygous for B.

So now let's do the dihybrid cross again. We have heterozygous for A and heterozygous for B. This is your male parent.

And then for your female parent, that's going to be heterozygous for A and then heterozygous for B. Again, same drill. Getting tired of this.

Let's try to identify the phenotypes. So this tells triangular and this tells triangular. So therefore, the shape of the seed capsule for...

Your male parent is triangular and then for your female parent, it's also triangular. So let's continue. I'm going to shut my mouth again.

And then you can move forward on identifying the gametes and then do the crosses in your own panet square. But then I would like to repeat the top gamete should just always be the male and then the side gamete should be your... female so let me do this on my own uh and do it also in your own notes and we'll check later and my bad that's wrong comment a recessive b recessive a dominant b i'm getting tired of this So okay we're done.

Now let's do the genotypic ratio again. This is getting it's 1, 2, 1, 2, 4, 2, 1, 2, 1. Now let's try to identify the general genotypes that we can get from this cross. We have the 9 of course a dominant A regardless of the second and a dominant B regardless of the second allele. We have 3 dominant A.

And then homozygous recessive for B. We have a homozygous recessive A. And then at least one copy of your dominant B. And then one homo recessive A. And then we have homo recessive B.

Where are they coming from? Again, look at the Punnett square. The 9 is coming from this.

That's going to be your 9. Your tree is actually coming from the encircled genotypes. The other tree is actually coming from the squared or rectangular genotypes. And the one is actually coming from the crossed out genotype.

So let's try to identify the phenotypes of these general genotypes that we have. So here we have a dominant A, dominant B. A saying triangular, B saying triangular. So this is going to be triangular.

And then this one, it's going to be triangular. This one is also triangular. But then this one is going to be ovoid. So in duplicate gene action, what is the phenotypic ratio that we are getting from this cross?

So if we do a heterozygous for both gene pairs, for the male parent and the female parent, the phenotypic ratio that we are getting in duplicate gene action is actually 50. is to 1. I hope you were able to get that. I think before we move forward to the next lecture, let's kind of like try to summarize what we have discussed for the last two lectures. So we actually discussed your gene.

I don't know why it became... Okay, so we discussed about gene. interactions.

So let me make it thicker. So we had gene interactions and in your gene interactions we have case number one, the first type of gene interaction, we have your novel phenotype. So that you will remember this for novel phenotype, what is the example that we used?

The example that we use here is the comb type in chicken. So for the comb type of chicken, we actually had four phenotypes. We have your rose, we have your pea, we have your walnut, and then lastly, we had your single comb.

But then what is our phenotypic ratio? Our phenotypic ratio in this type of gene interaction is actually 9 is to 3 is to 3. is to one. So hold on, nine is to three is to three is to one. The next, let's move to the second type of gene interaction.

We discuss your recessive epistasis. So in your recessive epistasis, the example that we had in here is actually the coat color in mice. So it's in your mouse. coat color and in your mouse coat color we actually had three we had your agouti which is dominant over your black but then we have a recessive allele which is actually causing albinism which is your white so therefore there are three colors that we can get so there are three coat colors we have your agouti we have your black and then lastly we have your albino So in here, our phenotypic ratio from this type of genetic interaction is actually 9 is to 3 is to 4. So after we finish recessive epistasis, we discuss your dominant epistasis.

But your dominant epistasis are actually divided into two cases. We have your dominant epistasis A. And in your dominant epistasis A, the example that we use here is actually your fruit color in summer squash.

So for the fruit color in summer squash, we actually had your white and then we have your yellow and then we also had your green. green. And then our phenotypic ratio in this type of genetic interaction is actually 12 is to 3 is to 1. After that, we proceeded to go into your dominant epistasis B.

And our example for your dominant epistasis B is the feather color in fowl. So for the feather color in fowl, we divided it into two phenotypes. They can be white or they can be colored.

And then our phenotypic ratio that we... Actually, head in here is actually 13 is to 3, wherein we have more white and then a few colored, which is actually 3. After dominant epistasis, we just finish covering from this session your complementary gene action or complementary genes. And for the complementary genes, The example that we had is actually your flower color in P.

And for the flower color in P, how many phenotypes did we have? We actually had two phenotypes. It can be purple, and then it can also be white or non-colored. So for the phenotypic ratio in this type of genetic interaction, it was actually...

9 is to 7. So these are the signatures for the different genetic interactions, the phenotypic ratios. And then lastly, we just finished covering your duplicate gene action or your duplicate genes. And our example for this type of genetic interaction is actually your shape of of seed capsule in shepherd's purse and it's very long seed capsule in shepherd's purse we have two phenotypes here the seed capsule can be triangular or it can be ovoid and the phenotypic ratio is actually 15 is to 1 so i think for the lecture on gene interactions. I'm gonna wrap it up here. Now we are moving forward to another lecture which is on pseudoalleles and I will be discussing that in a different session.

So you all have a great day.

Transcript for:Understanding Gene Interactions and Examples

Transcript for:
Understanding Gene Interactions and Examples