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Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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An Amaizeing Doubling Genome
31 August 1998 5:00 pm
The genomes of most animals are cluttered with mobile bits of DNA, called retrotransposons, whose origins are a mystery. Now a report in the September Nature Genetics suggests that retrotransposons can colonize and expand a genome surprisingly quickly. In just 3 million years, the study suggests, retrotransposons added enough copies of themselves to corn DNA to double the size of the plant's genome.
Over the last several years, researchers have come to realize that retrotransposons play an important role in evolution, expanding the sizes of genomes and, depending on where they insert, altering gene activity and function. "But before, we've never had a good feeling for how quickly and to what extent they can reorganize the genome," notes Dan Voytas, a molecular biologist at Iowa State University in Ames.
To begin to find this out, Jeffrey Bennetzen of Purdue University in West Lafayette, Indiana, and his colleagues analyzed the ends of 17 retrotransposons found in a region that they had sequenced a few years ago. Those ends, which can be 150 to 5000 bases long, are identical when the retrotransposon first sneaks into the genome. From that moment on, random mutations make them less and less alike. Bennetzan's team first determined that about 6.5 mutations occur annually per billion bases in this part of the corn genome. Based on the number of changes to the ends of the retrotransposons, they calculated that the retrotransposons entered the genome between 3 and 6 million years ago and over the ensuing millennia expanded that gene region from 80,000 bases to 240,000 bases, and the corn genome from 1.2 billion to 2.4 billion bases.
"We're surprised [the invasion] was so recent," says Bennetzen. "We would have guessed [the expansion] would have been more gradual, over tens of millions of years." Although they have no way of knowing what corn was like before this invasion, these retrotransposons paved the way for all sorts of new traits to evolve, he adds.