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3. Extensions to Mendelian Inheritance

Variations of Dominance



Variations on Dominance

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Hi in this video we're gonna be talking about variations on dominance. So there are many different types of dominance and the one that we've been referring to so far is called complete dominance. And that is any time a dominant allele is present, it's going to be expressed. So even it doesn't matter if it's Hamas I guess or if it's hetero, I guess you're gonna have the same phenotype. So Hamas I guess is not finna typically different than hetero I guess. So this is what the Planet Square normally looks like. You have a red flower. Here you go. It's homesickness dominant. You have a white flower, its home is like it's recessive. If you make them together, you get four offspring, they're all red, they look exactly like this parent because they have one dominant allele and then it looks the same as the two dominant alleles. This is what we're familiar with. This is what we've been talking about. This is called complete dominance. But genetics is very rarely like this, it's very rarely complete. So let's talk about some types of dominance that aren't complete. So the first one is incomplete dominance and this is when the number of dominant alleles affects the phenotype. So homos, I guess dominant is going to appear different than heterosexuals dominant. So this is if you do the same mating, so you have a red flower that's home as I guess dominant. And a white flower homicide is recessive when you make them together, you get four offspring each with one dominant allele and one recessive, but that doesn't look red instead, it looks pink. And that's because you're just getting one dose of the dominant allele. So what's the phenotype of the offspring from a red flower mating and a white flower mating under incomplete dominance? It's going to be pink. So it's gonna be pink. That question mark. It is pink. So that's incomplete dominance. A upper case does not look like a uppercase A lowercase. They're different types. Then the 3rd type is co dominant. And this is a really interesting example because there's usually two dominant alleles and both are expressed equally. So a good example of this is human blood types. We say it's the A. B. O. Blood type because some people have A some people have B. And some people have. So what this looks like is if you're actually looking at the genotype to get blood type A. You can have called I. A. And you can be homos I guess dominant for this gene or you can be heterocyclic dominant for A. And that will give you A. For B. It's the same except you replace the superscript A. With superscript B. And it can be home as I guess or hetero I guess. And you get B. Now the co dominance comes in here. Co dominance happens because what happens if you have one A dominant allele and one B. Well you get both proteins and that makes you type blood type A. B. And then if you're homicide is recessive meaning that you have neither dominant allele that you're classified as blood type O. So right here is the example of co dominance because there's two dominant alleles I. A. And I. B. And both are expressed giving you the A. B. Blood type. So if you were to mate a hetero zig asse blood type A. With a hetero ziggy's blood type B, you get one dominant allele and one recessive allele for each one. And so when you get four offspring you get this offspring, this offspring this offspring and this offspring. And so that produces four different types of blood. You can have Type A. B. Which is the co dominance because there's two dominant alleles you can have Type B. Because you have your blu l you can have type A. And you're a leo or you can have type O. Because there's no dominant allele present. So that's an example of co dominance. I feel people have hardest time understanding this one. Um But it's just that the fact that there's two dominant alleles and both are expressed equally. So with that let's now move on.

Which of the following is NOT a type of dominance?


Which of the following parents could produce offspring with an AB blood type?


Blood types are an example of what type of dominance?