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Chromosomal and Gonadal Sex: Inconsistencies

by Georgina Cornwall, PhD

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    00:01 Let’s look at where some of these issues can come up with inconsistencies between chromosomal sex and gonadal sex – XY females and XX males – seems like that wouldn't be possible and turns out that it very much is possible.

    00:21 So here we have a blown up version of the X and Y chromosomes and we have the pseudoautosomal region where crossing could happen.

    00:33 But if crossing over happens to happen outside of the pseudoautosomal region that means that all that stuff that’s important on the Y chromosome for development of male sex and sex characteristics could end up on the X chromosome which will present some interesting situations.

    00:56 So here we have a situation in which the SRY gene has been translocated through a crossing over event to the X chromosome which means that the X chromosome now carries the SRY gene and can produce testes determining factor and we have an X that could end up making a XX individual male.

    01:21 And then we could have a 46 XY individual that comes out female in the corresponding chromosome, we now have a Y chromosome that does not have an SRY and has some of the genes on it from an X.

    01:39 Those aren't such a big deal but the not SRY part is the bigger deal there.

    01:46 So, let's take a look at some of the inconsistencies that come up.

    01:51 These DSDs, disorders of sexual development – that’s how you'll see them presented early often.

    01:57 There are clearly multiple opportunities for things to go awry and have a DSD or disorder of sex development.

    02:06 We can see anything from complete gonadal dysgenesis meaning you have an XX individual that actually has developed as an XY individual, right? So full on male, full reproductive capacity, fertility and the works, but the chromosomes say that they are female.

    02:29 So I'll give you some insight unto like when do we really call someone male or female, is it about the X and the X or is it about the sexual development – lots of different questions to consider in there.

    02:43 You could also have mixed gonadal dysgenesis which would mean you know one of each – ovary and testis and depending on the battle between hormones and many other factors that would perhaps end-up creating two – one ovary and one testis or the ovotestis situation or we could go as far as having completely ambiguous genetalia, so a baby comes out and it has I don’t know, what sex is the baby? Hmm, that’s a good question.

    03:16 So it used to be that we would reassign not we because we weren't around then but doctors would reassign ambiguous genetalia always to be a female and that was because, well, frankly I guess it is easier to make a dysfunctional I mean a functional looking female that may not actually be functional.

    03:41 Now, we spend a little bit more time assessing where things may have gone wrong and so there are lots of different steps along the way to consider of what sex we might end up wanting to make the individual and sometimes it gets left a little later so that parents can have time to decide so definitely lots of different steps to consider along the way.


    About the Lecture

    The lecture Chromosomal and Gonadal Sex: Inconsistencies by Georgina Cornwall, PhD is from the course Chromosomal Disorders.


    Included Quiz Questions

    1. Translocation of sex-determining region Y onto the X chromosome
    2. Deletion of sex-determining region Y from the Y chromosome
    3. Translocation of sex-determining region Y onto the long arm of the Y chromosome
    4. Deletion of sex-determining region Y from the X chromosome
    5. Absence of the Y chromosome
    1. Deletion of sex-determining region Y from the Y chromosome
    2. Translocation of sex-determining region Y onto the X chromosome
    3. Translocation of sex-determining region Y onto the long arm of the Y chromosome
    4. Absence of the Y chromosome

    Author of lecture Chromosomal and Gonadal Sex: Inconsistencies

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD


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