I’ve explained, as far as is possible, this paper many times. Here’s another shot.
ncbi.nlm.nih.gov/pmc/articles/P…
ncbi.nlm.nih.gov/pmc/articles/P…
1. A 17 year old woman with no menstruation is examined and found to have no palatable gonads (no testes/ovaries) and a small uterus. Her karyotype was identified as XY.
This looks like Swyer Syndrome.
This looks like Swyer Syndrome.
2. Examination of this woman’s family history revealed, on her mother’s side, multiple family members with infertility, ambiguous genitalia etc.
Suggests she inherited her disorder from Mum, which is a bit odd, because her Mum is clearly fertile and apparently typical female.
Suggests she inherited her disorder from Mum, which is a bit odd, because her Mum is clearly fertile and apparently typical female.
3. All eyes on Mum, whose first blood test reveals she is also XY.
What’s going on?
Closer eyes on Mum, where it is found that her apparently normal ovaries are actually not all XY cells, but a small percentage (around 6%) X.
What’s going on?
Closer eyes on Mum, where it is found that her apparently normal ovaries are actually not all XY cells, but a small percentage (around 6%) X.
4. So Mum is a mix of karyotypes. The particular mix in her developing gonads has allowed ovaries to form.
One would not expect ovaries to form in a ‘predominantly XY’ gonad.
One would not expect ovaries to form in a ‘predominantly XY’ gonad.
But remember, this family is carrying a genetic mutation (unidentified) that messes with healthy testes development.
And we know in Turner syndrome, X females with X cells make ovaries.
And we know in Turner syndrome, X females with X cells make ovaries.
The result?
A Mum who, from her family history, we would predict has this as yet unidentified genetic disorder that does not support gonad development.
A Mum who, from her family history, we would predict has this as yet unidentified genetic disorder that does not support gonad development.
But a Mum who has, on top of that, undergone a separate genetic event in her gonads (the loss of Y to create a ‘low-level’ Turner karyotype) that has driven ovarian development
(and ensuing typical female internal and external genitalia).
It’s a remarkable coincidence.
(and ensuing typical female internal and external genitalia).
It’s a remarkable coincidence.
That’s why she had a paper written about her.
Here is a female who has ‘escaped’ gonadal agenesis (like we see in her family, including her daughter) by a second genetic event that has driven normal female development.
Here is a female who has ‘escaped’ gonadal agenesis (like we see in her family, including her daughter) by a second genetic event that has driven normal female development.
What do we learn?
Confirmation that Swyer (or ‘Swyer-like’) Syndrome can be stably inherited through families via some other mechanism than problems with the SRY gene on the Y chromosome.
Both Mum and daughter had a normal SRY gene.
Confirmation that Swyer (or ‘Swyer-like’) Syndrome can be stably inherited through families via some other mechanism than problems with the SRY gene on the Y chromosome.
Both Mum and daughter had a normal SRY gene.
We learn that mosaic karyotypes have unpredictable effects on sex development. Eg. What threshold of X ovarian cells would be sufficient to overcome the family trait of no gonad development?
We know that, in Turner Syndrome, the presence of cells in the ovary with typical numbers of sex chromosomes can support ovarian function.
We learn that it might not matter if those cells are XX or XY, just as long as they are healthy cells? That’s wild.
We learn that it might not matter if those cells are XX or XY, just as long as they are healthy cells? That’s wild.
Mostly, we learn that genetics can be freaky and awesome. 😂
*palpable, not palatable. 😂
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