Hi in this video, we're gonna be talking about pedigrees. So what is a pedigree? This is just a map of human matings. So generally geneticists do pedigrees and the reason that they do this is because somebody comes to them with some kind of disorder and they're like, what is going on? What is happening? Is this in my family, is this is this genetic and this person is called um this fancy name here? Preposterous. I don't know if I'm saying that right? So you have to forgive me if I'm not, I'm not super great at pronunciation, but this is the word and this is what you're gonna test. And so this is the first family member that comes to a geneticist and say, hey, I kind of want you to examine my family. I think there's something wrong. So pedigree is a map and maps. You have to understand the symbols. So I've given you a just cheat sheet here of different symbols. So here you have males, females mating. Um, parents and Children. There's twins. These are obviously non identical because it's male and female, they can be identical. Um and usually there's a notation that says that, but for the most part you probably won't be dealing with twins. Um, and then you'll notice that the effective male. So this is going to be a male with the disease or disorder that they're looking at is going to be black and the same for female and then sometimes you see these like half moon things, these are hetero zygotes for recessive. So their carriers essentially. So there's the other side, their carriers, there's death if it's crossed through and then generally the arrow represents the first person that came that fancy title for them. So when you're looking at pedigrees, you have to understand at least like mating and affected versus not affected. Um Most of the pedigrees you'll be dealing with are fairly simple. I'm gonna show you some examples of them, but you're gonna have to be able to understand and memorize these symbols. And so because in genetics and your tests, your quizzes and everything, you're going to likely be given some type of pedigree and then asked to identify the inheritance pattern. So what do I mean by inheritance pattern? I mean things like is it sex linked or not? Is it a dominant disorder? Is it a recessive disorder? Now I'm gonna go through and show you an example of all of these. Um Hopefully make it clear for you. But essentially that's what you're going to be given. You're gonna be given a question. Here's a pedigree, tell me what kind of inheritance is it, Is it dominant? Is it recessive? Is it sex length? So I'm going to help you figure that out. Let's turn the page

Okay. So now we're going to go over various auto iso melo pedigrees. So autism a means anything that is not in a sex chromosome. So autism, all mutations are autism. Mobile eels, they're all going to be on chromosomes that are not sex chromosomes. So they're going to be inherited in an auto iso melo fashion. So the first type of autism, all inheritance that we're going to talk about is autism, a recessive disorders. So autism a means not on a sex chromosome. And recessive means that in order to have the phenotype, you're going to need two recessive alleles. Okay, so here's an example of a autism, a recessive pedigree, and I'll disappear. So you can see it. And when you look at this pedigree, I want you to be able to identify that this is autism or recessive. So the way to do that, I've given you a few cheats here. The first thing is you want to look at how many Children come from affected or unaffected parents and then autism a recessive disorders. What you're going to see is that there are affected individuals. So fully recessive individuals that appear in the offspring of unaffected parents. Right? So they at least have one dominant allele. And so what we see here is that if we look at some unaffected parents, we can see that offspring are produced from unaffected parents. Right? Again, this happens again down here where we have an affected individual and two unaffected parents, that's the first thing that starts suggesting this might be recessive. Um, the second thing that shows us that it's probably oughta zonal is because the affected offspring occur in both males and females. If you start getting more females or more females, we start thinking that this might actually be a sex linked inheritance, but if it's pretty much males and females equally, then it is likely to be auto zonal. So if we look here, we can see that we have both females and males that are affected and although there's not a lot of affected, so it's hard to tell whether it's equal. We still can see that there's both males and females are affected. So it's likely autism a while. And then the third thing that suggests recessive is that there's only a few affected offspring. So looking at all of the people in this one family, there's only three out of several that actually have the disease. And so that's suggesting recessive. So autism, a recessive disorders, They're going to have affected individuals that show up in unaffected parents, it's gonna be males and females almost equally. And there's only really going to be a few that show up in an entire family. Okay, so now let's go and move on to autism all dominant. Now, autism will dominant is going to be a disorder that's caused from a mutation on a autos OEM, so not a sex chromosome and it's going to be a dominant allele. So it's gonna be an uppercase letter. Now, how we can tell this is through these little cheat sheets here. So the first thing is that the phenotype is going to appear in every generation. This suggests dominance, right? Because any time you get one dominant allele, that person is going to express the phenotype, right? It's gonna have the disease. Whereas an autism a recessive, you actually have to have two recessive alleles in order to have that phenotype. So dominant in a family is going to appear much more often than a recessive. Now if we have an effective parent we're going to have affected Children, okay, if you have more than one child, you're going to start seeing affected Children. So affected parents are going to pass it to their Children and that we're also going to see it equally, males and females, which is not written here, but we're saying males equals females. This suggests autism a while. And then one really unique part of this is because when we think dominant, we always think common, right? We say something oh that trait must be dominant because everyone has brown hair, right? It's sort of this sort of ingrained thing that you didn't actually learn, but you just think it's like that, but not as the dominant disorders is actually different because autism, all dominant disorders are rare. Now you may ask how in the world is a dominant disorder rare. Well if you have the r alil the uppercase r L l uppercase dominant allele then you're going to express that. But this khalil can be really rare in the population. So if you look at one individual family with this alil you're going to see that a lot of the people in that family are affected because it's the dominant disorder. But if you look at 20 families or 100 families or an entire population of families, you're gonna find that that Khalil is not present. It's very rare, it's very rarely present in any family. But if it is present then you're going to see it a lot. So autism all dominant disorders are dominant, but they're actually rare in the population as a whole. Okay, so here if we're looking at an autism, all dominant, what we can see is that affected parents have affected Children, Right? See this here. We can also see that it's pretty equally distributed among males and females. There's three males and three females here. We can see um we actually can't see that. It's it's rare in the population because if we look here, we're just looking at one family and it looks really common. But usually in questions like this, they'll say, oh this extremely rare disease shows up in this family. And if it was really that rare and autism will recessive, we would only see it in a couple of people in the family. But if its rare and dominant, then we see it, it looks like this. Okay. And that's an important distinction to make because there's a third type of pedigree, I want you to know about and this is called autism. A polymorphism. Okay, now polymorphism means that there are two or more common phenotype of a trait. So a good example of this is um Tasters are super tasters. There are people in the world that have more sensitive taste buds than others and it's actually fairly evenly divided. And you can test this through this um this little test you put a piece of paper on your tongue and if you taste it, you're super taste it. And if you don't taste it then you're just a normal taster. Now polymorphisms, it's not a mutation, it's not a disease, right? It's just a phenotype. Some people taste it and people don't, and that's okay. And these traits are inherited in a normal Mandali in matter and there's a lot of different ones. There's attached in free earlobes, there's widow peaks. This is the super tasters, they're just really common traits that you can have or you don't have. And it's not a big deal, it's not a disease, but autism. A polymorphisms are really common and they look really similar to an autism. All dominant. Um pedigree. So if we're looking here this is a pedigree for super tasters where if you don't taste it, your recess when you're black and if you do taste it, you're in white and your dominant, right? And we can see that we look here, we have an equal about equal number of males and females. We see that it's in every generation. So automatically looking at this, I'm thinking autism will dominant. But the way that I can tell the difference between autism a polymorphism and autism will dominant is that in the question you're given an autism will dominant, disease is going to be rare in the population. So autism will dominant equals rare in population. But common in a family, right? Because here we see it's very common in this family. It's pretty much in every generation, but it's rare in the population as a whole. An autism a polymorphism is going to be different because it's going to be common in the population and common in the family. Okay, now, most of the time you won't get a question about telling the difference between an autism a dominant and an autism a polymorphism. This would be a fairly advanced question, but I did want to include it just in case your professor decides to go over it. But most of the time, what you'll be comparing is is this an autism or recessive or is this an autism more dominant? And the way that you can tell that is looking through those cheat sheets that I provided above and will provide a really great flow chart at the end of this so that you can easily tell the part which pedigree is which. Okay, so those are the autism all pedigrees with that. Let's move on

Okay, so now we're going to talk about sex linked inheritance. So sex linked inheritance means that the disease allele, the mutant allele is going to be on a sex chromosome. So an X. Or Y. And that means that when you're looking at a sex linked inheritance, the first cue that it's a sex linked inheritance pedigree is that males and females are not represented equally, that there's either more males affected or more females affected. Usually it's more males affected. The reason for that is because males only get one X chromosome. So let me show you one. So the first one we're going to talk about is an X linked recessive X linked means that the mutation or the allele is going to be on the X chromosome. And recessive means that you either need two X chromosomes with the recessive allele to see it or one X chromosome and a Y chromosome for a male to see it. Okay, now X linked recessive orders or disorders are going to be much more common in males than females. Why? Because the male only needs one allele, right, It only needs that one X chromosome allele to have the disease. Whereas a female to actually express, it has to have two mutant X chromosomes. Right? So it's much more common for a male to get it because they only need one. So let's look at a pedigree and let's look at some of the cues that will tell you that this is an X linked recessive disorder, the first thing is more males are affected, which I just explained why it's because males only need the one X. Whereas females need two exes The 2nd 1 is that an affected male parent will usually not have affected offspring. The reason is because if you have a mutant male so this here is the mutant most of the time females hardly ever get this. So most of the time in these crosses your mating with a homo zegas recessive female. And what's going to happen is that all the suns will get the X. From their mother and that's not going to be effective and all the daughters will get one X. From their mother and one X. From their father. But because it's recessive they're also not going to be affected because they're going to be hetero Ziegenfuss. So an effective male parent will not have affected offspring if they're mating with a homo zegas recessive mother. This is most often the case. Now this statement does not hold true if you're doing this cross. Right, okay. So if you're crossing an affected male parent with a carrier mother, right with the one recessive allele because there is a chance to produce this offspring and this offspring. Okay but this is very rare. Okay most of the time this doesn't happen. So this is going to be the case most of the time. Which is why I said an affected male parent will not have affected offspring but all the daughters will be carrier. So what you'll see is that when the daughters are carriers then in the second generation, what you see is this because we have affected daughter mating within another affected male and that produces affected offspring. So I'm gonna show you an example of this. So another clue is that the sons of affected males do not pass it to their offspring. And an example of this is red green color blindness. So let's look at this pedigree. We have an affected male. So what their genotype is is that right mutant allele here? Now most of the time you're going to mate with a homesickness mother right? Who doesn't who's not a carrier carriers are fairly rare. So then we have all unaffected offspring. Right now this would not be the case if we had this cross. Right? And that cross could potentially happen right? Because we know that the the daughters of this cross all are getting this X. This mutant X. From their father. So this daughter is going to be a carrier and this daughter is gonna be a carrier. Now if either of these carriers mated with an effective male. So you have this cross which would be X. R. X. R. Y. Then what you would get we can actually just write out the punnett square here you get what you get half normal females, half normal males. Half mutant females and half mutant males. Right? So half of your males would be wild type and half would be mutant and half of your females would be wild type and half would be mutant. Okay, but this is not the case. Like I said, these types of meetings are fairly rare. So what happened in this pedigree is we had an affected father made it with a homogeneous recessive mother. The daughters were carriers. But because these diseases fairly rare, they made it with nor normal males. And so they had Children. And these Children had a chance of getting that right, because the mother is a carrier and can pass that to their offspring, which in this case they did. Now this one is the one that confuses most people and it's clear why. Right? Because there's all these different cases. So when you're looking at an X linked recessive disorder, the first thing that I want you to do is quote one or more females than males affected or more males than females. Effective. If there's more males automatically start thinking excellent recessive, the second one is we start looking at the combinations, right? Because if it's X linked dominant, then this male is going to pass it to their offspring. But if we start seeing that affected males are not passing it to really any of their offspring thinking recessive. Okay, and then it's easy if you actually start riding out the X chromosomes to figure it out. Now, I'm also going to include at the very end of this topic a flow chart to help you figure out whether it's excellent or autism or excellent processes, excellent dominant. And that will help you walk through how you do this as well. So now let's talk about excellent dominant now, excellent dominant. We're going to see it in a lot more Children. Right? If you just look at these pedigrees without even knowing anything, we see it every generation, there's a lot of people in this family affected very different than what we see up here with the excellent recessive. So, excellent dominant. We're going to see that affected males pass the condition to all daughters and no sons. So let's look at this, right, We have an effective male. So it's going to be a dominant disorder, right? Excellence is going to be an X chromosome dominant. It's going to mean one allele is needed. We have an unaffected mother. So now what's going to happen? Well, they're going to have affected daughters, right, Which we see here, they can have unaffected sons. All of their sons are actually going to be unaffected because they get the X chromosome from the mother and the wife and the father. So because the mother is unaffected, the sons are going to be unaffected, but all the daughters are going to be affected because that X chromosome is going to be given to every daughter. So we see all the daughters affected no sons. Now, if we look at Hetero Zegas females which are now this generation here who mate with unaffected males, right? They are going to pass it to half of their offspring, right? Because if we do this punnett Square, so we have an affected mother. Hetero ziggy's mother, we have an unaffected father that's gonna be an affected female, this is gonna be an unaffected female, this is going to be an affected male and this is going to be an unaffected male. So hetero ziggy's females mating with unaffected males pass it to half of their offspring. Okay, just from Mendel in genetics. So if we look from the other perspective now we have a female um mating with a male and unaffected male it's going to be X. Ry slower case. And then most of the time these are gonna be hetero, Zeke is not home as I guess. Okay and we can see that this heterocyclic female mating with an unaffected male produces it and half of their Children. So we have these 12 are affected and these two are not and then we can carry it on an affected male is going to pass it to all daughters. But no sons, which is what we see a hetero I guess female is going to pass it to half of the offspring. So by looking at the generations and taking males and females differently, we can easily break apart an X linked dominant disorder. Now excellent. I know they're more complicated but stay with me and stay with me to that especially to that flow chart because the flow chart is really going to help you be able to narrow down what these things look like. And then the last one is a wide linked disorder. So this is going to be a mutation on the Y chromosome. And what you can see is that only males inheritance. So if you see a pedigree where only males are having the disease, no females at all and it seems to be fairly common, Every male gets it essentially right. It's going to be passed on with every male in the family getting it. That's going to be a Y link disorder. This is very rare. It's going to be unlikely for you to get a question on a wide link disorder, on a quiz or a test. Usually they're overlooked because they're so extremely rare. You're really never going to see it. Okay, so that is those are the X linked to the sex linked disorders including excellent, dominant X linked recessive and Y linked with that. Let's turn the page, get to that flow chart and help you understand how to differentiate all these pedigrees. If you're looking at a pedigree on a quiz or a test. Okay, so with that, let's move on

Okay, so now I have made this pedigree flow chart and I want to walk you through it because I think it's going to be helpful. So often you're going to get a pedigree on a test or a quiz and you're going to say, you know, what type of inheritance pattern is this? Now I gave you some ways to figure this out, but that can be really difficult to memorize and answer in a question and a test test or quiz. Not a quest even though it can sometimes be a quest to get that grade. So, um, I made this flow chart and you can just answer these questions about the pedigree you're seeing and it'll lead you to the appropriate inheritance. So the first question it says, do all affected individuals have an affected parent? Yes or no. If it's yes, you go on to answer this question. If it's no, you go on to answer this question, you've repeat this. So here we'll follow this one. Does this trait affect mostly males? Yes or no? If no, it's autism or recessive. If yes, you answer this the same thing over here. Do all affected males have an affected mother? Yes or no? Yes. Does the affected father produce daughters who are all affected? Yes. And you keep answering these questions and eventually you will get to your answer, what type of pedigree is this? So I suggest if you have some problems in the back of the book or if you are studying for a quiz or a test or you know, even just pedigrees that you may see in your textbook or even the pedigrees that I showed you above. Just take one and walk through through this pedigree flow chart and see if you can figure out, you know what sort of inheritance it is. And that way, if you can't really remember all the individual characteristics of each pedigree, if you can remember this flow chart, then that will really help you getting those questions right? And understanding how to look at a pedigree and know which inheritance pattern it is. So hopefully this flow chart will help you. But with that, let's now move on.