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17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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Chromosomes Born of Broken DNA
6 January 1998 8:00 pm
We inherit our genes thanks partly to DNA "handles" called centromeres that help a cell gently pry apart pairs of chromosomes, allowing them to be passed on to a daughter cell. Now scientists for the first time have witnessed a fragment from a damaged chromosome somehow sprout a centromere and get copied. The findings, reported in this month's Nature Genetics, might someday help researchers get a handle of their own on aberrant chromosome diseases and to make artificial chromosomes stacked with healthy genes for treating diseases such as cystic fibrosis.
In their efforts to pinpoint the positions of centromeres on fruit fly chromosomes, a team led by Gary Karpen of the Salk Institute in La Jolla, California, blasted flies with gamma rays, which broke the ends off of some of the chromosomes. Curiously, as the fruit fly cells divided, some of these chromosome fragments were passed down through dozens of generations to daughter cells.
Karpen's group suspected that a new centromere had formed on the fragments, allowing them to be pulled apart and copied. To test this idea, they showed that the new chromosomes would stick to a fluorescent antibody that binds to proteins that attach only to centromeres. Karpen argues that the gamma rays somehow transformed part of the original chromosome's DNA to a form that can develop a centromere. He speculates that before the chromosome's end broke off, the radiation first caused an DNA inversion, bringing the end near the centromere-forming regions. Karpen speculates that the centromere either added a protein or altered the structure of the chromosome end, thereby giving it the ability to become a centromere.
"It is tremendously thought-provoking," says Huntington Willard, a geneticist at Case Western Reserve University's School of Medicine. "A sequence that shouldn't have any idea how to be a centromere has been taught to adopt that role." If geneticists can learn how to turn any DNA into a centromere, that may help gene therapy researchers, who are currently trying to build artificial chromosomes that can deliver curative genes to patients with a genetic disease, Willard says.