Scientists first discovered chromosomes in the late 1800s, after the light microscope was invented. Using these microscopes, biologist Walter Flemming observed many tightly wound, elongated structures in cell nuclei. Later, it was found that chromosomes are made from DNA, the cell’s genetic material.
Since then, scientists have proposed many possible ways that DNA molecules might fold into 3-D condensed chromosomes. Now, researchers at MIT and the University of Massachusetts Medical School have obtained novel data on the 3-D organization of condensed human chromosomes and built the first comprehensive model of such chromosomes.
In this model, DNA forms loops that emanate from a flexible scaffold; the loops are tightly compressed along the scaffold. “This is a very efficient way of packing DNA material,” says Leonid Mirny, an associate professor of health sciences and technology and physics at MIT and a senior author of a paper describing the findings in the Nov. 7 online edition of Science.
Computer simulations courtesy of Imakaev I.M., Fudenberg G., Naumova N., Dekker J., and Mirny L.