Biology

Genetic study finds biological sex is more complicated than just chromosomes

Genetic study finds biological...
Researchers have found extra pieces of the puzzle that determine biological sex in embryos
Researchers have found extra pieces of the puzzle that determine biological sex in embryos
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Researchers have found extra pieces of the puzzle that determine biological sex in embryos
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Researchers have found extra pieces of the puzzle that determine biological sex in embryos
Researchers have found extra pieces of the puzzle that determine biological sex in embryos
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Researchers have found extra pieces of the puzzle that determine biological sex in embryos

It's generally understood that the biological sex of an embryo is determined by the chromosomes at conception – two X chromosomes will develop as female, while an XY combo will become male. But this simple rule may be too simple. A new genetics study out of Australia has identified extra pieces of the puzzle that could explain some disorders of sex development (DSD).

The Y chromosome dictates male development through certain genes: it carries a gene called SRY, which in turn ramps up activity on another gene known as SOX9. High levels of SOX9 triggers development of testes in an embryo, creating a biological boy.

In the new study, a team from the University of Melbourne and the Murdoch Children's Research Institute investigated this mechanism in more detail. The researchers set out to check how the SOX9 gene was regulated by segments of DNA known as enhancers, and how disruptions to these enhancers could lead to DSD conditions.

"We discovered three enhancers that, together ensure the SOX9 gene is turned on to a high level in an XY embryo, leading to normal testis and male development," says Andrew Sinclair, lead author of the study. "Importantly, we identified XX patients who would normally have ovaries and be female but carried extra copies of these enhancers (high levels of SOX9), and instead developed testes. In addition, we found XY patients who had lost these SOX9 enhancers, (low levels of SOX9) and developed ovaries instead of testes."

These enhancers were found among what has in the past been referred to as "junk DNA." Although this makes up about 90 percent of human DNA, it has historically been overlooked because it doesn't contain genes. But that doesn't mean it's useless, as studies like this highlight. With about a million enhancers regulating the activity of about 22,000 genes, clues to new treatments could be hiding in this so-called junk DNA.

"These enhancers lie on the DNA but outside genes, in regions previously referred to as junk DNA or dark matter," says Sinclair. "The key to diagnosing many disorders may be found in these enhancers which hide in the poorly understood dark matter of our DNA."

The research was published in the journal Nature Communications.

Source: University of Melbourne via EurekAlert

6 comments
highlandboy
So yet again “junk DNA” is found to have a very real purpose. I’m still amazed that biological science has attributed certain DNA to the “junk” category just because they do not yet know it’s purpose. In physics and non-organic chemistry the not knowing drove scientists to theorise and test in order to explain what they didn’t know. To not theorise and test seem to be laziness in the extreme. Yes it’s complex, yes it’s hard to test - but isn’t that what makes finding out worthwhile?
amazed W1
This research is potentially social dynamite. It could lead to the all female society, so much in demand these days, with biological sexuality being switchable when it was felt that greater diversity in parenthood was desirable. This assumes the current efforts at reproduction from two different XX sources remain unworkable..
Lucke
"Junk DNA" was used to name a thing we did not know what it was... It makes us happy and going on... :))
Ranscapture
Life uses too much energy to keep “junk” around. If you don’t use something, it goes away. Obviously there isn’t ANY junk dna.
ljaques
Peer reviewed in Nature Communications, so it has to be real, huh? Give the Leftists credit for faking more science to go along with their 1,000 gender claims. The claim that much of our DNA is junk just proves the expanding hubris. God help us when people no longer believe in true science.
Jean Lamb
And, to be honest, the X and the Y chromosome aren't always straightforward--sometimes there's something called a 'mosaic' or in English, a mess.