"Intersex" is somewhat of a misnomer. Human genome is XX or XY. And there are people who have genetic issues where they have XXY , (fragile X syndrome)
No that is Klinfelters syndrome, fragile X is when a there is a mutation in the FMR1-gene.
or XYY (Jacob's syndrome) - both these syndromes the child is considered and usually "assigned male" at birth. Also though portions of X or Y chromosomes can end up in places where they are not suppose to be; thus they produce birth defects of the genitalia. But truth remains that in human beings; you either have a Y chromosome or you don't. "Y" is "male".
Now there is a very small number of males who have a genetic defect where their bodies don't respond to testosterone. And so in utero; they do not develop male primary sex traits. And when that is the case the "default" development is "female". But these males don't have ovaries or a uterus either. And because their bodies do not respond to testosterone, they will not go through puberty either. But one would need a genetic test to know if this is the case. Thus what is generally done in these cases is the child is given estrogen at puberty; because... giving them testosterone isn't going to work anyways!
Yes, those with complete androgen insensitivity don't develop male primary or secondary sex characteristics. They are widely seen as women across the world. Even without estrogen replacement
Then there is an XX genome with a piece of a Y attached to it which produces a "female" with "male genitalia".
It is called translocation. If the SRY-gene (which determines most of the differentiating int to the male phenotype) gets translocated on to the X chromosome we can say that they are XX SRY+ (positive).
(She basically has ovaries, a uterus and a penis; but some of these girls also have a scrotum and their ovaries actually drop into the scrotum and thus they appear "male" at birth.
Eh, where have you read that most has ovaries and a uterus? That was not in textbooks from what I can remember. The normal presentation is phenotypically male with small testes, but with out producing sperm.
I don't know whether or not some of these girls can bear children; but some of them clearly can't.
Are you sure that it is common for them to have a uterus?
They do not produce testosterone though because they do not have a Y chromosome. (Their gonads are ovaries, not testicles; even if they are in a "scrotum" and they do produce estrogen because they are genetically coded XX.)
They do produce testosterone, but often at a lower level. They don't produce estrogen, normally.
Thus the estrogen will produce breasts and a "feminine" body.
What? The normal presentation is male.
A lot of these girls aren't recognized until puberty because they look like boys at birth and develop normally; (I.E. they don't usually have other health or developmental issues) thus, there's no reason to do a genetic test if no one suspects anything.
Many of them are not even found at puberty (contrary to what you have said here they go through male puberty normally), but in fertility investigations (they don't produce sperms). Some are never discovered.
This genetic defect (X chromosome with Y genetic material attached) comes from the father's production of sperm. In meiosis; some of the genetic material that would produce "Y sperm" ends up in "X sperm". This is not that common though.
Approximately 1 in 20000 boys.
There also exists individuals that are XY SRY-, with an external female phenotype (normally with an uterus and fallopian tubes but no functioning ovaries).
It was ten years I read about this so take my statements with a grain of salt, but I couldn't leave your post uncommented since there seems to be some misunderstandings in it.
@BCP1928 I'm not sure that what was presented in the post I just quoted is entirely correct (I saw the informative reaction).