 All right, I'm going to give you a color blindness problem. Can you see the number in there? It's illegal for me to diagnose you as color blind. But this is like Ishikara's color blindness plates that they use to diagnose whether or not you are color blind. Mmm, the plot thickens. All right, here's your problem, are you ready? With a color blind man, man makes a bebe with a woman who's a carrier, a carrier woman, what is the phenotypic ratio of their possible babies? Like what are all the possibilities for babies that they can make and what is the phenotypic ratio for that? Okay, so what are you going to do first? I've given you the phenotypes. That part of your Punnett square problem solving toolkit done. So what's the next step? Genotypes, dogs? So color blind male, what's his genotype? Well, we know he's an XY because he's a he. And we know that he's color blind, which means he has to be carrying the recessive allele, done. How about the carrier lady, what does that tell you? If she's a carrier, means that she doesn't express it, otherwise they just tell us she's got two Xs, but she's a carrier, so she's actually heterozygous. We could have said she's a heterozygous female, but we can also call her a carrier. What's my next step? We've got to make some gametes. Let's go through meiosis. Please, if you would like, review meiosis to make sure you understand how we end up with these gametes, but we're just going to segregate through the process of meiosis, and we're going to end up with one sperm that contains an X and one sperm that contains a Y. These are all my possibilities. And in Lady Land, we're going to get a big X, oops. There we go. That was a good rescue operation. We've got a big B and we've got a little B on our two X chromosomes. Who determines if your baby is a boy baby or a girl baby? That would be the fellas. So if ladies, your fella ever tries to claim that you are responsible for whether or not you have a boy child come out of your body, you can call bold duty duty on that as well, because sorry, fellas, you control that. You got to have some Y chromosome swimmers if you want to get a boy baby, or you can have some X chromosome swimmers to get a girl baby. I don't have any of those. All right, let's throw our gametes in here. Little B, XY, this is my fella. X big B, X little B. I've got XY over here, but there's no X, it's only a Y. Now, let's combine some sperm and eggs just for the fun of it. I always put my big Bs first because my brain just likes to read it that way better. But look, what kind of babies are these? 100% girl babies, do you agree? Now we've got some stuff going on with our girl babies, so we're going to have to look closer, but those are all my girls. Those are all my boys. Check it, my friends. Let's see, what are our phenotypes? 50% girl, 50% boy. That's going to be the case all the time. But of my boys, I mean my boys, half of my boys, half of my kids are going to be non-colorblind kids, and half of my kids are going to be colorblind. However, what's true about her? She's a carrier, and that's going to be relevant for if she has a boy baby in the future because all of her boy babies, do you agree with this? We'll have a 50% chance at being colorblind. That's interesting too. All right, clowns, I think that that is your example of a sex-linked problem. So we're going to go look at some other chromosomal issues that are possible.