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20. Quantitative Genetics

Analyzing Trait Variance


Analyzing Trait Variance

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Hello everyone in this lesson, we are going to be learning about how to analyze trait variants. Okay everyone. So traits obviously vary. You can have different phenotype for different individuals for the same particular trait. Now, trait variants can be determined by many factors it can be termed by genetic and environmental factors and most of the time it's going to be both bow, both environmental and genetic factors are going to be contributing to the particular phenotype that an individual has. And to understand mathematically which gives which amount of variance. So how much genetic variance matters in the phenotype and how much environmental variance matters in the genotype? We have this formula and V. P. Means the variance in the phenotype or the variants in the trait that you were looking at. And then V. G. Is going to be the genetic variants the variants in the gene, a types of the individuals which types of alleles do they have? How much do they vary across the population and then V. Is going to be the environmental variance. So how much does the environment vary? How much does that matter towards the phenotype of the individual? So whenever you look at genetic variants and environmental variants you want to know, how much does this contribute to the variants that we see in the phenotype because some jeans or some traits are very different. Some traits are determined greatly by the environment. Some traits don't care at all about the environment and our only determined by genetic variants. So it is very interesting to look at where the variants comes from in a particular trait. Now to determine the variation attributed to genetics only. What are you going to control for? Well, if you want to know exactly how much variance only comes from the variants in the genomes, Well then you should have no variance in the environment. So you should control for environmental variance. So you should make the control have the control environment. So the environment should be the same exactly the same for all of your test subjects, but your test subjects can have different gina types. So if you are looking for how much genetic variation contributes to, let's say, stem height in flowers than what you would do is you would plant multiple seeds of one species in a carefully controlled greenhouse. So this is going to allow you to have zero environmental variants because they are all in the exact same environment. They all have the exact same environment. They do not vary in their environment. So there is no environmental variance and you're going to have multiple seeds from one species. But these gina types of these seeds vary. So they have genetic variants. So whenever you're looking at the trait or phenotype of stem height and you want to know how much variance and stem height relates to the variance in the genotype, you simply control for the variance in the environment. Now, what if you wanted to do the exact opposite of that, what are you going to do? Well to determine the variation attributed to the environment. You must control for genetic. So how much environmental variation contributes to the stem height of these flowers? You're going to plant multiple, genetically identical seeds. These are going to be clones of one another, and then you're going to try out different environmental conditions. So you're going to allow the environment to vary, but not the genotype of these individuals. So there's going to be no genetic variants. And this is because they all have the same genotype. They are clones of one another. So they're all genetically the same. There's no genetic variants, but you can put them in different environmental conditions. Maybe some plants are outside, inside in the rain, in the sun in the shade, You can change it up. Right? So, a representation of these types of experiments can be seen here. So, let's look at the first one, which is going to be environment variation. So if you're looking for environmental variation or how much variation in the environment contributes to the phenotype, you need to have all the same individuals. So these are clones of one another and you guys can see that because there's only one genotype, only one genotype and that genotype is the a genotype. So all of these individuals, you guys can see all of these plants have the exact same genotype, they have the a genotype. They are clones of one another, but each of these individuals is in a unique environment. So they all have a unique environment. So maybe the first one here lives in the shade but it's given a certain amount of water and then this one here lives in the sun and is given a certain amount of water or this one's in the cold, this one's in the heat, Their environment is changed and it's going to see how the phenotype varies. And obviously because the height is different for these individual clones, the environment does have some effect on the variants that we see in plant height. So yes the environment in that particular graph does have effect on the variants in the plant height. If it didn't if it had no effect you would see something like this where all of the plant heights were exactly the same. What you could glean from that is that there is only genetic variants that matters in the phenotype of these individuals. The environment does not have any control over the expression of plant height. If we had no effect from the environmental variation, that is what it would look like. But our graph is different. So obviously the environment does vary the phenotype a bit. Now this one here where we're doing the opposite. This is genetic variation. So how much genetic variation contributes to the variation in the genotype. Now you guys can see that they all have. So they all have unique gina types. All of these gina types here are unique. We have an individual A. B. C. D. E. F. G. And H. They all have unique gina types so they're not genetically the same. They are not clones but they all have the same environment. All have the same environment. So for this experiment V. E. Equals zero. For the other experiment V. G. Equals zero. And they're testing how much genetic variation contributes to phenotype variation and how much environmental variation contributes to phenotype variation. And as you guys can see the different genotype do have different heights. So yes, genetic variation also has some effect on phenotype variation. So those are going to be the different types of variation that you can look at for the variation in a trait. And remember you can always do this formula to see how much the environment and how much the genetics vary and how they contribute to the variation in the phenotype. Okay everyone let's go on to our next topic.

Which of the following represent trait variation caused from genetic variation?


If you wanted to identify what proportion of trait variation is due to the environment, you would do what?


If you wanted to identify what proportion of trait variation is due to genetics, you would do what?