 Our first set of unique inheritance phenotypes, expressions that don't match what we would expect, given our understanding of Mendelian patterns, deal with how the dominant trait or the dominant allele is expressed. So we're going to look at two new ideas and they relate to dominance. So we have incomplete dominance and co-dominance and both impact the phenotype expressed from a heterozygous genotype. We're going to compare all of these. I think it's a little muddy. Oh, I have a feeling I'm going to be saying that a lot in this lecture. I want to include what's normal, what do we call what we've been seeing? I'll tell you what it is. We call it complete dominance. Dominance. That says complete dominance. That makes me think of my brother. And if you know my brother, you will know why I said that as compared to incomplete dominance and co-dominance. Okay, those are the three things we're going to compare. And look at our definition again. The key that we're looking at here is what do we see when we have a heterozygous genotype? So I'm going to throw in some letters just for the fun of it. Like let's use the letter A and we're talking about heterozygous genotypes. So look, all situations we're talking about heterozygous genotypes. In fact, let's do this. Let's say genotype. So we'll make this into a chart. I like it. Our genotype in the chart. And then let's throw in our phenotype into this chart because the phenotype is what gets weird with a heterozygous genotype. All right. With complete dominance, what do you see? What happens when somebody has a heterozygous genotype? They express the dominant trait 100% of the time. All heterozygodes that in when Mendelian patterns show complete dominance, they will express the dominant trait even though they have that recessive allele. This is key to our understanding of Punnett squares and predicting offspring. We know that heterozygodes express that dominant trait unless the trait isn't completely dominant. It's incompletely dominant. In incomplete dominance, the phenotype that is expressed is it's almost like it's half. It's like a fraction expresses the dominant or I don't even like that. I want to say it's an intermediate, but then that's going to mess this up with co-dominant. So we have to be a little bit careful. An intermediate expression. The way that you think about this is I'm just going to give you an example. If you had red flowers and white flowers and your red flowers are big R, big R, and white flowers are little R, little R, and you get your heterozygous big R, little R, and that guy has pink flowers. You end up with, you're not fully red, but you're sort of red because you're pink. You have this incomplete expression of the dominant or what you would expect to be the dominant phenotype. Now, I'm going to write down pink flowers so that you can remember, but the distinction between incomplete dominance and co-dominance is a little tricky. In co-dominance, now think about this incomplete, like you're not quite expressing fully. Like you need two copies to fully express the dominant phenotype. If you only have one, you can only get like partway there pink flowers instead of red ones. With co-dominance, both alleles, both phenotypes are equally expressed. So in that case, now I think of spots whereas white and red mixed to make pink. It's an intermediate. If you have blobs of both, you fully expressed both alleles. You have red spots and white spots, and that's a full expression of both alleles. The next thing we're going to talk about is multiple alleles, and that's an example. We'll have another example of co-dominance in that section that I think is probably the best example of incomplete dominance that we have, but we're going to use it to talk about a different concept. Okay, I probably won't ask you to distinguish between incomplete dominance and co-dominance unless it's the example that we're doing next with blood type.