Since its discovery, biologists have compared DNA to a book that contains the instructions for making a cell’s proteins. But if a genome is text, it is badly edited. Most DNA is gibberish, full of stutters, snippets of doggerel from other species, and echoes of quiescent viruses. In humans, only about 2 percent of the genome encodes proteins. Much — but not all — of the remaining 98 percent is evolutionary detritus. In the 1960s, researchers learned that non-coding DNA can serve vital functions, such as regulating gene action and building ribosomes. The remainder they began to call junk.
Today, junk DNA is at the heart of the most radical transformation of how we understand the genome since the information metaphor. Three books — The Deeper Genome by John Parrington, Junk DNA by Nessa Carey and Biocode by Dawn Field and Neil Davies — present a vision of the twenty-first-century genome. Their relative success hinges on metaphor and imagery, both in how they conceive the genome and in the writing itself.
In September 2012, the ENCODE (Encyclopedia of DNA Elements) consortium announced that its multi-year international effort to catalogue the various types of DNA sequence had assigned “biochemical function” to 80 percent of the human genome. Incautious reporters began shouting that junk was bunk, even though scientific consensus maintains that most genomes contain large amounts of it. The subsequent debate upregulated public interest in non-coding DNA — but how do we talk about DNA now?
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