Sex Chromosome Aneuploidies

by Georgina Cornwall, PhD

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    The critical thing here to understand is lots of different conditions can arise even though chromosomally an individual may appear to be male or female. Many things could happen along the way. All of those things that we’ve previously considered are chromosomal structural changes. Now, we’ll step into the sex chromosome aneuploidies or polyploidies. The interesting thing is that sex chromosome aneuploidies and polyploidies can be tolerated much more easily than aneuploidies of autosomes. It seems that the dosage, just the right amount of gene product isn’t such a big issue. Well, I’m sure that you can probably answer the question why at this point. Think to yourself, what is it that’s different about the sex chromosomes than the autosomes? First of all, you know that there’s an X and an X, and an X and a Y. We’ve already certainly talked about the idea of dosage compensation. Aneuploidies of X chromosomes are fairly common actually because of the dosage compensation piece, right? So, you’ll recall that because a male has an X and a Y and females have X and X, in order to make the dosage similar between the sexes, the extra baggage or whatever on the X chromosome has to be hypermethylated and condensed. It condenses into a Barr body. We’ve certainly talked about this a number of different times. But it’s because of this dosage compensation that the X chromosome aneuploidies or polyploidies in fact could be much more easily tolerated. Because what happens, as you can see in these images is that the number of inactive X's, so let’s say we have a polyploidy, we have three X's or even four X's because nondisjunction happened twice. We can actually see up to six or eight X's and have a viable child born. That is because...

    About the Lecture

    The lecture Sex Chromosome Aneuploidies by Georgina Cornwall, PhD is from the course Chromosomal Disorders.

    Included Quiz Questions

    1. Dosage compensation with X inactivation
    2. Deletion of extra X chromosomes
    3. Duplication of extra X chromosomes
    4. Dosage compensation with X destruction
    5. Dosage compensation with X conversion into Y
    1. Inactivated hypermethylated X chromosome
    2. Activated hypermethylated X chromosome
    3. Inactivated hypermethylated Y chromosome
    4. Inactivated hypomethylated Y chromosome
    5. Activated hypomethylated X chromosome
    1. Ovarian maintenance
    2. Development of internal genitalia
    3. Development of external genitalia
    4. Production of progesterone
    5. Production of testosterone

    Author of lecture Sex Chromosome Aneuploidies

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD

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