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Top Story

Knotty problems in DNA

If you’ve ever tried to untangle a pair of earbuds, you’ll understand how loops and cords can get twisted up. DNA can get tangled in the same way and in some cases has to be cut and reconnected to resolve the knots. Now, a team of mathematicians, biologists and computer scientists has unraveled how E. coli bacteria can unlink tangled DNA by a local reconnection process. The researchers developed computer software, with DNA represented as flexible chains, to model the possible locations where reconnection enzymes could cut and reconnect the chains. Overall, they modeled millions of configurations representing 881 different topologies, or mathematical shapes, and identified hundreds of minimal pathways to get two DNA circles linked in up to nine places down to two separate circles. The computer model confirmed the biologists’ hunch: Undoing one link at a time is the preferred route to separate the circles of DNA.

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