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3. Extensions to Mendelian Inheritance

Overview of interacting Genes


Interacting Genes Overview

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Hi in this video we're gonna be talking about the overview of interacting genes. So genetics is very rarely clear cut so far. We've been talking about, you know, very clear examples of dominant and recessive and things like that. But that's really very rarely the case because many traits that we have actually exist on a range. So for instance it's not that just somebody is tall or short. We have this huge range of heights. Someone can be the same as for weight, the same as even for hair color. These things like are not just darker, light, taller, short, it's usually a range. And so when it is a range of course the genetics are going to be more complicated than just dominant and recessive. So this video is just an overview of a few different terms of ways that genes can be more complicated than them. So the first one I want to talk about is polly genic, polly genic means that a trait is controlled through multiple genes. And so if you have multiple genes controlling one trait then you're going to get a continuous expression. Things like height. So let's look at an example of what that would look like. So for this example we're looking at a plant and this plant is purple, purple and white. And so there are two genes that control this plant's color. We have P. One and P. Two. So let's do this crossing here. So we get a dominant and recessive for P. One. So hetero zegas and we're hetero ziggy's for P. Two as well for both um for both parents. So we're hetero zig asse for both traits for both parents. So when we do this cross, I'm not gonna write it, I'll just go ahead and give you the answer, I'll disappear. So you can see if you wanted to practice punnett squares feel free, go ahead. Um So the first thing we're gonna get is if we get a home as I guess or hetero Z guess for both genes. So we have at least two dominant alleles right, then we get two doses of the dominant allele and that creates this dark purple. If we end up with homosexuals or heterosexuals for one gene, so for instance p. one. So we have this one dominant allele but this one is going to be um homesickness recessive, then we only get one dose of the purple gene. And so we end up with light purple. The same is if we're focusing on gene to where this one is dominant and this one is recessive, we still just get one dose and that's light purple. And then if we end up homicide is recessive for both, Then we end up with zero doses and we end up with white. So the number of dominant alleles for every gene determines the dosage of how many genes you have. So if you have one dominant allele you get one dose if you have two dominant alleles you get to if you have three dominant alleles you get three, so on and so forth. And that's going to determine the exact color. With the more dominant alleles being darker color and the less dominant or the less there are dominant alleles, the more light it will be. And if there are no dominant alleles it'll be recessive completely and be white. So this is how we get one way we get a ranges through just multiple genes infecting doses. How many doses of dominant do you have? So that's apologetic and that's really all I'm gonna say about apologetic but there are lots of other ways that genes can interact together and we're gonna spend time on each one of these. So I'm just introducing the definitions here and then each one of these things will get its own video and where I'm going to describe exactly how this works. So in the case of multiple genes of something being poly genic controlling a trait, they can interact in different ways and when they interact in different ways that's going to cause different phenotype and those phenotype will be on ranges. So one example, one definition here is play a trophy and so apply a trophy. Apply a topic. Gene is going to be a single gene that has different multiple different effects on the phenotype type of an organism. You may be confused. You may say well okay let's just focus on gene a well wouldn't gene a do the same thing and that organism throughout its entire life. And the answer is no some genes are activated. Um maybe when you're born and then when you're 80. Right? And so um when you're born that gene is going to have a very different effect on your body than when you're 80. And so jeans their function can change as you get older. Their function can change as you gain weight. Their function can change as you're exposed to different things in the environment. So genes can have multiple effects on the organism phenotype. That isn't just one single gene. It can have different effects in different cell types for instance or different organs. So it's a single gene with multiple different effects on an organism. We have variations on dominance which is something you've probably actually heard of before. Um You talked about probably very briefly in an intro class talked about incomplete dominance or co dominance with blood types. So this is an example of variation of dominance. And so this just describes how dominant alleles affect the feel. Type two. Remember with blood types, blood types are an example of co dominance where if you have an a dominant allele and a B dominant allele you can have A. And B. Blood types can be blood type A and B. So that's an example of variation on dominance and well there's a whole video on just dominance. So don't worry if you're not completely sure on it now a third one is called a pistol Asus. And so episode Asus is all about how to genes interact and how those interactions affect the phenotype. And there's lots of different ways. So before I describe those doses but it doesn't always work out like that. And there are some really unique and complex ways genes can interact to produce phenotype. So this is gonna be a really long and complex topic but it's also something that you're going to get tested on a lot. So whenever you watch this episode basis video make sure you give yourself some time to learn it. Like go ahead and prepare to take some time to spend some time on this video because it's gonna be long. It's gonna be a lot to memorize and a lot to sort of take in. Um So to make sure whenever you're ready to sit down and learn about stasis and gene interactions you give yourself some time. The 4th 1 is gonna be penetrates. And that is um actually the people with an illegal that expressed the phenotype. So how many people. So not every alil is expressed and not every allele is expressed to the same extent. So there are lots of people in the world who all have the same alleles but not all of them expressed that alil and so penetrate it looks at how many of the people with a certain level actually express it who's a little bit different than the rest of them. And then expressivity measures instead how well that allele is expressed. So there's lots of people with this a leo but not everybody expresses it to the same strength. Some people express lots more of it and they get you know, a really strong phenotype and then other people with the exact same allele expressed less of it and get a weaker phenotype from it. And so that measures how that Aaliyah will be expressed, how much of it will be expressed. So like I said, each one of these is gonna get its own video. Um There's lots to talk about for each, every single one of these. But this is just the basic definitions of how genes can interact um to cause complex phenotype. So with that let's move on.

Which of the following terms describes an interaction between two genes?


Polygenic traits are controlled through which of the following ways.


Polygenic traits are usually continuous traits?