Not junk DNA, Zimmer says

Book author and Discover blogger Carl Zimmer criticizes those who wrote about a recent Science paper, saying essentially: “Enhancers aren’t junk DNA, and nobody who knows what enhancers are ever thought so.”

They took their cue from the headline of the press release. Oops.

An enhancer is essentially a control button on the DNA determining when a certain gene gets turned on or not. Most of the time, scientists find enhancers somewhere near their favorite gene, while trying to figure out what pieces of DNA can account for where and when it gets turned on.

Junk is a word that more accurately describes a pseudogene (it looks like a gene, but it doesn’t work anymore) or a repeating element (debris from a kind of internal virus), not an enhancer.

In this recent case, it seems they found the enhancer first, without knowing what gene it controls. More precisely, they found it by computer, comparing human and monkey DNA to find sequences that were highly conserved in vertebrates but had rapidly evolved in the transition from monkey to human.

This particular piece DNA makes embryos turn blue in interesting places. Evo-devo coolness.

Whoever wrote the press release (at Yale, even) called the enhancer junk, and the scientists who did the work let it go by. Perhaps they figured that something inexact was OK if it got some attention. Or maybe they thought people would understand “once thought of as junk DNA” as meaning decades ago rather than months ago.

Having people misunderstand something in a way you didn’t anticipate is a typical problem faced by a science writer!

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