46,XX Karyotype: Disorders

by Georgina Cornwall, PhD

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    Now, let’s consider disorders associated with an XX karyotype. Chromosomally, the individual is XX but it may not come out there phenotypically. Most of all, as you would expect, we will see that there is a translocation of the SRY gene from the Y chromosome and onto the X chromosome. If the X chromosome has an SRY gene just as we would expect from normal sexual development, the primordial gonad will become a testis because there’s the SRY gene being expressed as testis determining factor. We will see development of testis and ideally testosterone and then production of male external genitalia. In the cases where we have an SRY gene, generally everything proceeds as normal male sexual development. However, we call them XX testicular DSD's because we see that there are testes developing. Now, there are some cases where we don’t see an SRY gene present at all. So, it wasn’t translocated from the Y chromosome to the X chromosome. We essentially have two normal X chromosomes. Some of these patients have ambiguous genitalia that suggest evidence of male sexual development. But how is that even possible when there’s no SRY gene? That’s a really great question, a pretty active field of research presently. But the evidence that we see is that even though the genitalia may be ambiguous, they have cryptorchidism. So, there are definitely testes but they’re undescended or hypospadias in which the urethra hasn’t made its way all the way through the penis. So, it’s located just below the penis and it’s just not normal. Male development looks ambiguous. One of those who knows what. Another condition we see, even smaller percentage, will have both testicular and ovarian tissues. So, this is where we might answer the question about true hermaphroditism because surely if you have one...

    About the Lecture

    The lecture 46,XX Karyotype: Disorders by Georgina Cornwall, PhD is from the course Chromosomal Disorders.

    Included Quiz Questions

    1. Disrupted production of hormones
    2. Wastage of salt
    3. Infertility
    4. Hypotension
    5. Hyperpigmentation
    1. 80-85%
    2. 15-20%
    3. 35-40%
    4. 60-65%
    5. 90-95%

    Author of lecture 46,XX Karyotype: Disorders

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD

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