Has anyone ever made a list of all the Darwinians who insisted that all that DNA was just a vast heap of junk, left over from evolution? There is a book in that. Meanwhile,
Researchers have known for years that satellite DNA is highly variable between species. “If you look at the chimpanzee genome and the human genome, the protein coding regions are, like, 98 percent, 99 percent identical,” she says. “But the junk DNA part is very, very different.”
“These are about the most rapidly evolving sequences in the genome, but the prior perspective has been, “Well, these are junk sequences, who cares if your junk is different from mine?'” said Jagannathan.
But as they were investigating the importance of satellite DNA for fertility and survival in pure species, Yamashita and Jagannathan had their first hint that these repetitive sequences might play a role in speciation.
When the researchers deleted a protein called Prod that binds to a specific satellite DNA sequence in the fruit fly Drosophila melanogaster, the flies’ chromosomes scattered outside of the nucleus into tiny globs of cellular material called micronuclei, and the flies died. “But we realized at this point that this [piece of] satellite DNA that was bound by the Prod protein was completely missing in the nearest relatives of Drosophila melanogaster,” Jagannathan said. “It completely doesn’t exist. So that’s an interesting little problem.”
If that piece of satellite DNA was essential for survival in one species but missing from another, it could imply that the two species of flies had evolved different satellite DNA sequences for the same role over time. And since satellite DNA played a role in keeping all the chromosomes together, Yamashita and Jagannathan wondered whether these evolved differences could be one reason different species are reproductively incompatible.Eva Frederick, Whitehead Institute for Biomedical Research, “So-called ‘junk’ DNA plays a key role in speciation” at Phys.org
A friend writes to say that it appears that taxonomically restricted (“orphan”?) DNA was important to the process.
Too bad PePe LePew got Canceled. He’s the poster skunk for the species problem: