 Okay, sometimes you have multiple alleles, and this can complicate different heredity patterns. What this means is that you have one gene, and we've been looking at two alleles, but you can have more than two alleles. I wanted to use the greater than, less than sign, but my brain can't do that on the fly. Which way does the little arrow go? I don't know. Blood type. Here we are. I'm going to draw you a blood cell. And my blood cell, your blood type, exists because you have little protein substances called antigens embedded in the cell wall of your red blood cells. So this would be an example of an antigen. And look, the blood type gene, for whatever reason, why did they do it this way? I have no idea. It's the I gene, codes for these little antigens. So if you have the I gene, you're going to have some kind of, well, never mind, let's just say the I gene codes for these specific antigens in red blood cells. Now, I'm going to tell you all the multiple alleles. You would expect you have IA, which codes for A antigens. You can have IB, which codes for B antigens. Does that work for you? And you can have I, baby I, recessive I, which codes for no antigens. Now, check it out. I'm going to draw you a blood cell. And you tell me right now what antigens, what is the genotype of this blood cell right here, the one I've drawn right now. Do you see any antigens on it? No. So the genotype has to be, I agree, little I, little I. The reason why it was codominant is because we've fully extre- we've got AB blood. This guy is AB blood. That guy is O, type O blood, because it doesn't have any antigens on it at all. Okay, does that work for you? The multiple alleles are significant because it just increases the number of different categories or situations that you can have. So tell me, if I have type B blood, what does my blood cell look like? Type B blood has B antigens on the blood cell. Do you agree with that? What is my genotype? Well, I've got to have IB to get those B antigens. What else? I could have two IBs or I could have IB, little I. Both of those result in the same B blood phenotype. Right? I think that's it. What? That's crazy talk. We can actually talk about doing things like determining whether or not your mother is your mother based on blood type, mixed up babies in hospitals. Yeah. Then you can figure out which baby goes to which mama based on blood types. Yeah. Start thinking about that fun stuff, not mixing up your baby at the blood, whatever, figuring it out, being a sleuth, being whatever that's called person who puts babies back with their mamas. There's another one, polygenic traits. Try and guess what it is before we get there and then I will tell you all about it.