Repurposed transposon parts are at the very heart of what makes humans human, says Gennadi Glinsky, a cancer biologist at the University of California, San Diego. Some of the control switches transposons once used for their own hopping have been recycled over time into useful tools that help species, including Homo sapiens, adapt to their environments or take on new characteristics. Many researchers used to think these broken transposons were just genetic garbage.įar from junk, however, jumping gene remnants have been an evolutionary treasure trove. The majority are in bits and pieces scattered throughout the genome like so much confetti. Most of the transposons in the genomes of humans and other creatures are now “dead,” meaning they are no longer able to jump. Corn is an extreme example, but humans have plenty, too: Transposable elements make up nearly half of the human genome. One strain of maize, the organism in which Nobel laureate Barbara McClintock first discovered transposable elements in the 1940s, is nearly 85 percent transposable elements ( SN: 12/19/09, p. Fossils of the DNA parasites build up like the remains of ancient algae that formed the white cliffs of Dover. Genomes of most organisms are littered with the carcasses of transposons, says Cédric Feschotte, an evolutionary geneticist at the University of Utah in Salt Lake City. She studies how jumping genes have influenced fruit fly evolution. “You cannot understand the genome without understanding what transposable elements are doing,” says González, of the Institute of Evolutionary Biology in Barcelona. They are parts of our genomes - like genes. She doesn’t think of transposons as foreign DNA. Bacteria have transposable elements,” says evolutionary biologist Josefa González. “Transposable elements have been with us since the beginning of evolution. This chart shows a breakdown of the major contributors. The human genome is nearly half jumping gene DNA.
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