 Now, hopefully, it's always interesting to try and evaluate your own genetic background or your history. And we can't really legitimately just go around making babies to see what they'll look like and do little genetic tests on ourselves and learn about our own genetics. So one of the tools that humans use are their pedigrees. And a pedigree is basically a bookkeeping tool to help you visualize inheritance patterns and hopefully figure out what your genetics or what your genotype might be. So a pedigree, it's a chart. Here's the deal. Circles are females. And of course, squares are male. Of course, somebody who makes a baby with someone else is connected. Somebody who's married to someone else is connected by a, what, horizontal line. If babies are made from the union, then you end up with another little line that comes down illustrating all the babies that are made. Usually, you make a pedigree following, tracking one characteristic. And if the circle or square is colored in, this is someone with the affected phenotype. So anytime you see a fully colored in person, then you know that they have the condition. They're expressing or displaying the condition. If you see someone that's half colored in, that usually indicates that they are a carrier of the condition. So they're heterozygous. Often, you will be given a little bit of information, but your job will be to figure out like what could be true about these people. And sometimes there's more than one answer to this little situation. I wonder, I just made this thing up. So I wonder if I can figure it out. Let's see what we can figure out from this particular pedigree. So first of all, you don't know unless you're told, okay, this is a pedigree for colorblindness. If we're told that, we know colorblindness is a sex-linked recessive condition. But what if we weren't told anything about this condition? Because I don't know anything about it. We could actually look at this and see what we can figure out. What we would know is that these are our questions. We would want to know is it sex-linked or autosomal. We don't know the answer to this. We also want to know if it is a dominant or recessive condition. Is this, okay, so this person obviously has it. Could it be a dominant condition? Could it mean, now think about that for a second. Let's just say it's autosomal. Let's pretend like it's not sex-linked at all. And we'll just make an assumption that it's autosomal and we'll try it out and see if it works. If it's autosomal, now we're just going to randomly say, okay, let's call it, let's use the letter B. And just for the heck of it, let's see, could it be dominant? This is our hypothesis. If it was a dominant trait, it would mean that you would be affected if you had the trait. But can you be a carrier if the trait is inherited dominantly? No. And you know what else? If this person had a big B and therefore had the trait, then where did they get that big B? You'd have to get it from mom or dad and neither one of them are affected, which means this definitely cannot be a dominantly inherited condition. The key, if you're looking at, okay, what kind of inheritance pattern does this condition have? The key is to see, do the parents have it? And if the parents have it and the kids have it, then it might be dominant. So this could not be a dominant inheritance situation. Okay. So then our question would be, could it be, let's see if it could be autosomal recessive. In which case we would need two copies to be affected and here we'd need to be a carrier because I showed you that this person is heterozygous. So now think about this. If this person is expressing it, where did she get her little Bs? She had to get one from mom and she had to get one from dad. Are they expressing it? No. So they also have to have big Bs to give, not only so that they don't express it, but also to give to their kids. Do you see how that works? Just out of curiosity because I'm kind of curious, is it possible that it is sex-linked? If it is sex-linked recessive, then she has to have two copies, which means she has to get, this is awesome. She has to get one of those from mom and one of those from dad. So mom would have to have, she isn't, mom isn't expressing it, but she'd have to have at least one copy. But dad? Look, if she's got it, dad has to give her a little B and if he gives her a little B, he also has a Y. That would mean he would have it. So could it be sex-linked? No. Dude, how awesome is that? It's like this great problem-solving adventure. There's lots of problems available online that you can look in our resources list and find some examples of some problems that you could go practice on pedigrees and I'm sure we'll do some in class. I think that's everything. Yeah. Bye now.