Figuring out which genes are active and which aren’t – in, say, an organ or a group of cells – is critical for both basic biological research and the development of treatments for diseases like cancer. Researchers at the University of Texas Southwestern Medical Center have developed a way to simultaneously assess, for a given biological sample, the activity of all the genes in the genome, based on how tightly their DNA is wound. DNA spends much of its time coiled up; when a gene is turned on, its segment of the coil unwinds. Biophysicist Harold Garner says he has devised a way to separate coiled DNA from DNA that’s “loose and free.” His team then uses DNA microarrays to determine which genes are in the open group – and therefore active. The technique could help uncover the secrets of a host of diseases, Garner says. The researchers, for instance, are using it to find out how cancer drugs affect gene activity. “This will allow us to hopefully tune some of those drugs and identify new drugs that may work better,” Garner says.