The Mysterious ‘Jumping Gene’ That Appears 500,000 Times in Human DNA
14th August 2018
For years, Miguel Ramalho-Santos tried to convince researchers in his lab to study a segment of DNA he personally thought was quite extraordinary: LINE1. It’s repeated half a million times in the human genome, making up nearly a fifth of the DNA in every cell. But nobody in his lab wanted to study it. “It was sort of a running joke in the lab,” says Ramalho-Santos, a developmental biologist at the University of California at San Francisco.
It might have had something to do with LINE1’s reputation. “People have called it junk DNA,” says Ramalho-Santos. “People have called it genomic parasites.” LINE1, like other transposons (or “jumping genes”), has the unusual ability to copy and insert itself in random places in the genome. Geneticists tend to pay attention when LINE1 inserts itself in a bad place, causing cancer or genetic disorders like hemophilia. But Ramalho-Santos suspected there was more to LINE1. If LINE1 were at best harmless and at worst harmful, why would it persist—and in such abundance—in the human genome?