Transposons, or "jumping genes," make up roughly half of the human genome. Geneticists previously estimated that they replicate and insert themselves into new locations roughly one in every 20 live births.
New results, published in the June 25, 2010 issue of Cell, suggest that every newborn is likely to have a new transposon somewhere in his or her genome.
"Now it looks like every person might have a new insertion somewhere," says senior author Scott Devine, PhD, associate professor of medicine at the University of Maryland School of Medicine's Institute for Genome Sciences. "This is an under-appreciated mechanism for continuing mutation of the human genome."
The research was initiated at Emory University School of Medicine, where Devine was in the Department of Biochemistry. First author Rebecca Iskow, PhD (now a postdoctoral fellow at Brigham & Women's Hospital in Boston) was a graduate student at Emory. Two other papers on human transposons appear in the same issue of Cell.
Transposons resemble e-mail spam: short repeated sequences that have no obvious function other than making more of themselves. The full name for the type of transposon that is most abundant in the human genome is retrotransposon. The "retro" term comes from how they replicate: first, the DNA is transcribed (copied) into RNA, and the RNA is reverse-transcribed into DNA again. This process normally only happens during very early in development, when the cells that will become eggs and sperm have not turned down a separate path of differentiation.
"Transposons are the original selfish genes, and this strategy makes sense for them, because it makes sure new copies will get carried into the next generation," Devine says.
While working in Devine's lab as a graduate student, Iskow devised a technique for "amplifying" the stretches of individual genomes that border transposons and reading thousands of the junctions with advance
|Contact: Vince Dollard|