A key to the mystery of fast-evolving genes was found in ‘junk DNA’

A long-standing puzzle in evolution is why new genes — ones that seem to arise out of nowhere — can quickly take over functions essential for an organism’s survival.

A new study in fruit flies may help solve that puzzle. It shows that some new genes quickly become crucial because they regulate a type of DNA called heterochromatin. Once considered “junk DNA,” heterochromatin actually performs many important jobs, including acting like a tightly guarded prison: It locks up “bad actor” genes, preventing them from turning on and doing damage.

Heterochromatin is also one of the fastest-changing bits of DNA in the body, so the genes that regulate it have to adapt quickly just to keep up, evolutionary biologist Harmit Malik at the Fred Hutchinson Cancer Research Center in Seattle and his colleagues report online November 10 in eLife.

“The work is a milestone,” said Manyuan Long, an evolutionary biologist

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