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Most people know that DNA contains genes, which hold the instructions for life. But scientists have long known those genetic blueprints take up only about 2% of the genome, and their understanding of what’s going on in the rest has been murky.

Similarly, they have known that the genome contains regulators that control the activity of genes, so that one set of genes is active in a liver cell and another set in a brain cell, for example. But the new work shows how that happens on a broad scale.

It’s “our first global view of how the genome functions,” sort of a Google Maps that allows both bird’s-eye and close-up views of what’s going on, said Elise Feingold of the genome institute.

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While scientists already knew the detailed chemical makeup of the genome, “we didn’t really know how to read it,” she said in an interview. “It didn’t come with an instruction manual to figure out how the DNA actually works.”

One key participant, Ewan Birney of the European Molecular Biology Laboratory in Hinxton, England, compared the new work to a first translation of a very long book.

“The big surprise is just how much activity there is,” he said. “It’s a jungle.”

The trove of findings was released in 30 papers published by three scientific journals, while related papers appear in some other journals. In all, the 30 papers involved more than 500 authors. The project is called ENCODE, for Encyclopedia of DNA Elements.

We are finding way more switches than we were expecting

The human genome is made up of about 3 billion “letters” along strands that make up the familiar double helix structure of DNA. Particular sequences of these letters form genes, which tell cells how to make proteins. People have about 20,000 genes, but the vast majority of DNA lies outside of genes.