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General Biology

Learn the toughest concepts covered in Biology1&2 with step-by-step video tutorials and practice problems by world-class tutors

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13. Mendelian Genetics




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In this video, we're going to introduce epistolary, sis and Soe. Epistolary sis is another type of inheritance pattern where one jeans product, a fax, the phenotype of another gene. And so, in other words, epistolary. This is when one gene effects another gene, and so, as an example, we're going to take a look at EPA Stasis and blood type. And so, in human blood type, there is an H protein, and this H protein serves as a connector molecule, and its role is literally to connect or attach a and B molecules to the surface of red blood cells. And so the recess Ivo Alil for this h protein with lower case H, it actually encodes an inactive form of the H protein that does not work. And it does not connect a or B to the blood cells as it's supposed to. And so what this means is that even if the person has the ah Leal's capital, I A or capital, I be they will actually have blood type O. If they are homos, I guess recess it for the H protein because again, the H protein is what's necessary to attach the A and B molecules, and so, without a functional H protein, the person will have type o blood, regardless of the illegals that they have. And so, in other words, what we're saying here is that one gene, which is the H gene, is going to affect the expression of another gene, which would be the capital I or capital. I be jeans. Now, although episode aces applies with both I A and I B and our image down below, we're on Lee going to be looking at the example as it applies to I A. And so in this example down below, we can see how EPA Stasis can cause inconsistencies in inheritance of blood types. And so what you'll notice is we have the genotype here in the first column of this image and the FINA type over here in the second column of this image. And previously, what we had seen is that any individual that has capital I A in their Gina type, regardless of what the second olio is, even if it's another capital I A or even if it's, ah, lower case I or even if it's a capital, I be regardless of what this one is uh, if the individual had a capital I A, then they would have a molecules on their surface, and this is true, but it requires the ah functional H protein. And that means that the individual must have at least one capital H for their H protein so that that connector molecule works properly. And so in this scenario, when they have this particular Gina type, that means that they will have an active H protein that works properly and again. The H protein is basically represented by these black connector lines, which are again required in order for the A molecule to be expressed on the surface. And so, if you have an active H protein, then the, uh a molecules will have no problem being attached to the surface. And that means that the individual will have blood type A, as we already have discussed in our previous lesson videos. Now, what we're introducing new here is that if the individual has to lower case, H is if they are homo zegas, recess it for the H protein. That means that they're going to have an inactive form of the protein that does not connect A or B molecules, and so over here with the two lower case, H is now, instead of having an active H protein, it has an in active H protein that does not work and so notice that the connector molecules are no longer here. And without the's connector molecules, the A molecules cannot be attached to the surface of the red blood cells. And so it turns out that the phenotype of these individuals, even though they do have capital I A just like these individuals, do they actually end up having type O blood? And that is because again, one because of a prosthesis, because of the fact that one gene, which is the H gene for the H protein, is affecting the expression of another gene, which is the capital I a gene here in this scenario and so ultimately EPA Stasis is just when one jeans product effects the phenotype of another gene. And so this here concludes our introduction to EPA Stasis, and we'll be able to get some practice as we move forward in our course. So I'll see you all in our next video

Which of the following statements best describes epistasis?