The cells in our bodies contain carefully packed strands of DNA that are about 6 feet long. Job Dekker, a biologist at the University of Massachusetts Medical School, says how the strands are folded hold clues to our health and well-being.

We each have about 20,000 genes, all of which sit together on a molecule of DNA. One of the great discoveries of the 20th century was how the shape of DNA allows those genes to work. Each DNA molecule is actually a pair of strands wound together, forming a double helix. To make a protein from a gene, a cell must separate the strands and read their sequence. To reproduce, a cell must rip the strands apart and build new counterparts for each one.

Biology textbooks teach these fundamental rules of life with a simple diagram showing DNA looking like an abstract spiral staircase. But reality is far messier. Each DNA molecule is six feet long. Our cells have to wind it tightly to fit in their interior — without tangling them in knots in the process. In fact, our cells have to unfold and refold DNA in order to read their genes.

In recent years, scientists have made tremendous progress in reading the sequence of our DNA. But the three-dimensional shape of DNA remains mostly mysterious. In fact, it’s only recently that scientists have even begun to get a glimpse at how our DNA is folded.

SCIENCE HAPPENS! By  CARL ZIMMER