From at ScienceDaily:
Mammals will develop ovaries and become females unless the early sex organs have enough of a protein called SOX9 at a key stage in their development. SOX9 causes these organs to become testes, which then direct the rest of the embryo to become male.
The amount of SOX9 produced is controlled initially by the SRY protein encoded by the Sry gene, which is located on the Y chromosome. This is why males, who have an X chromosome and a Y chromosome, usually develop testes while females, who have two X chromosomes, do not.
Only 2% of human DNA contains the ‘code’ to produce proteins, key building blocks of life. The remaining 98% is ‘non-coding’ and was once thought to be unnecessary ‘junk’ DNA, but there is increasing evidence that it can play important roles.
The latest study adds to this evidence, showing that a small piece of DNA called enhancer 13 (Enh13), located over half a million bases away from the Sox9 gene, boosts SOX9 protein production at the right moment to trigger testes development. When the team genetically removed Enh13 from male (XY) mice, they developed ovaries and female genitalia.
It’s not the first time sex has been reversed in mice but it is the first time a non-coding region triggered the change.
“Our study also highlights the important role of what some still refer to as ‘junk’ DNA, which makes up 98% of our genome. If a single enhancer can have this impact on sex determination, other non-coding regions might have similarly drastic effects. For decades, researchers have looked for genes that cause disorders of sex development but we haven’t been able to find the genetic cause for over half of them. Our latest study suggests that many answers could lie in the non-coding regions, which we will now investigate further.” Paper. (paywall) – Nitzan Gonen, Chris R. Futtner, Sophie Wood, S. Alexandra Garcia-Moreno, Isabella M. Salamone, Shiela C. Samson, Ryohei Sekido, Francis Poulat, Danielle M. Maatouk, Robin Lovell-Badge. Sex reversal following deletion of a single distal enhancer ofSox9. Science, 2018; eaas9408 DOI: 10.1126/science.aas9408 More.
Junk DNA played the same role in defending Darwinian evolution as claims that Neanderthal man was a subhuman did: The vast library of junk genes and the missing link made Darwin’s story understandable to the average person and the missing link even became part of popular culture. With Darwinism so entrenched, the fact that these beliefs are not based on fact will be difficult to root out of the culture. Darwin-only school systems are part of the problem.
Note: One junk DNA defender just isn’t doing politeness anymore. In a less Darwinian science workplace, that could become more a problem for him than for his colleagues.
See also: At Quanta: Cells need almost all of their genes, even the “junk DNA”
Was Neanderthal man fully human? The role racism played in assessing the evidence
“Junk” RNA helps regulate metabolism
Junk DNA defender just isn’t doing politeness any more.
Anyone remember ENCODE? Not much junk DNA? Still not much. (Paper is open access.)
Yes, Darwin’s followers did use junk DNA as an argument for their position.
Another response to Darwin’s followers’ attack on the “not-much-junk-DNA” ENCODE findings