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About two meters' worth of DNA is crammed into a nucleus that's only some five micrometers to 10 micrometers wide, and though how it's arranged in there influences gene expression, Science News' Sarah Schwartz writes that researchers have only recently been able to begin to tease apart genomic architecture and how it shifts over time.

Researchers like Baylor College of Medicine's Erez Lieberman Aiden and his colleagues have found that though strands of DNA may look like a knotty mess, the chromosomes are actually specifically arranged, Schwartz says. "Each chromosome contains clusters of genetic material that get close enough, bundling together, to interact," she adds. "These groupings can also engage with nearby clusters from other chromosomes."

Folding, she notes, enables far-off DNA regions to interact. For instance, using their Hi-C approach, Aiden and his colleagues have developed spatial maps of genome, finding thousands of loops. Similarly, the University of Michigan's Indika Rajapakse is using 3D-FISH to label DNA in three dimensions to glimpse the geometry of the genome.

But, Schwartz adds, genomic architecture is ever changing, prompting researchers like Aiden and Rajapakse to analyze genomic structure over time.

"The scientists hope that mathematical analyses of the genome will identify important 4-D differences between various cell types and between healthy and diseased cells," she says, adding that nucleosome disruptions have already been linked to some disease.