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X-linked Dominant Inheritance

by Georgina Cornwall, PhD
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    Now, let’s move on into X-linked dominant inheritance. Again, I’ll emphasize that it can be hard to pick out especially because of the concepts of penetrants, how many people are actually expressing the genotype and the phenotype. Sometimes there are issues with expressivity. Is the disorder actually being expressed in its full range or is there a continuum of expression? It turns out, because of features that we’ve already discussed, there can be a big range of expression. But in classic dominant relationships for X-linked, if you have a father that’s affected as you see here, you’ll notice that none of the sons of an affected male are affected. You check this out. You can see that only the daughters of affected males are affected. That is because transmission from male to male is impossible because the male gives the Y chromosome. If the disorder is anywhere in the two X’s of a female, they will express it. Now, we’re going to examine some more complexities or things that throw a wrench into the situation. Is it possible for an X-linked dominant trait to be only expressed in a female? Now, as we’ve just reviewed, it can certainly show up in males. But are there conditions where it only shows up in females? The answer is of course because anything can happen. The example here is of male lethality. If the condition is lethal prior to term then the fetus will be spontaneously miscarried and only the females would show up. That’s the case with Rett syndrome which we’ll examine in a little bit more detail later. But Rett syndrome is a rapid onset of symptoms. It’s in females because it is lethal in males. We only see Rett syndrome in females. It’s X-linked dominant but there are no males...

    About the Lecture

    The lecture X-linked Dominant Inheritance by Georgina Cornwall, PhD is from the course Single-Gene Disorders.


    Author of lecture X-linked Dominant Inheritance

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD


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