Sex-Linked Inheritance Example 1

by Jason Amores Sumpter
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So here we have an example Problem that's asking, What is the inheritance pattern of the following pedigree? Over here, on the right hand side on. We've got these five potential answer options down below. Now, right off the bat, we know that we can probably eliminate Answer Option E. Since we didn't really talk a lot about why linked disorders, uh, in our previous lesson videos. Now next, one of the first things that you want to try to do to eliminate any of the X linked disorders, um, is to look at the distribution of the, um disorder across males and females. And so when you count up all of the individuals that are affected and not affected, which will realizes that there are five females that are affected and there are seven males that are affected and again the females are shaded circles, the affected females are the shaded circles, and the affected males are the shaded squares. And so there are five shaded circles and seven shaded squares, and so that's pretty close to each other. So because there's not a massive distribution here between males and females, then we might eliminate the X linked, uh patterns of inheritance. So that limits us to either an autism will dominant or an autism will recess of patterns of inheritance and recall that one of the key features of autism will dominant is that it is found in pretty much every generation. It tends to be found in every generation. And so when you look across generation one, you can see that it is certainly found. Here. You look across generation to and at first glance it does seem to be found in this generation. But which will realizes that this individual number seven here is not actually linked vertically to these parents. Which means that this individual seven is actually coming from another family. And so really, what we can see is that there has been a skip in the generation for the individuals that are connected vertically here. And so, Ah, skip in the generation is a symbol of, or a sign of autism will recessive. And it turns out that this is actually the case for this problem. And so what you can see is that the disorder is in generation one. It skips generation to, and then it's found in generation three and down below here. You can kind of see over here that it skips this entire side over here. This generation and the only reason that it may not have skipped over here is because there was an individual that was also affected that came into play. But again, this is how we can also determine that it is. Autism will recess now. Another way to check for this is we know that autism or recessive means that it's going to have, um, Thean Vivid Jewel's must be Hamas. I guess recessive in orderto have the disorder and so you could just put in some, uh, letters in here to figure this out. And of course, the individuals that are not affected must have at least one dominant khalil. So you could do that throughout, and then just see if this holds consistency throughout the entire thing, and you could perform pedigrees to check to ensure that it is actually possible for this pattern of inheritance to exist throughout this pedigree. But again, the easiest ways to just check for these clues, such as this skipping of a generation or the presence of the disorder in every generation. And so this year concludes this example, and we'll be able to get some more practice applying these concepts as we move forward in our course, So I'll see you all in our next video.