Two American scientists were jointly awarded the Nobel Prize for Medicine or Physiology on Monday for their groundbreaking work on how genes behave. Victor Ambros and Gary Ruvkun discovered microRNA, which the Nobel Assembly describes as "a fundamental principle governing how gene activity is regulated." The tiny microRNA molecules play a crucial role in determining how different cells — which have the same chromosomes, essentially their instruction manual — have different characteristics. "The answer lies in gene regulation, which allows each cell to select only the relevant instructions," the Nobel announcement said. But subsequent work, including the discovery of another microRNA in 2000, proved that there are more than a thousand genes for different microRNAs in humans.

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Persons: Victor Ambros, Gary Ruvkun, Ruvkin, Silverman, Worcester , Massachusetts Ruvkun Organizations: Medicine, Nobel, Massachusetts Institute of Technology, Natural Science, University of Massachusetts Medical School, Harvard University, Harvard Medical School Locations: Hanover , New Hampshire, Worcester , Massachusetts, Berkeley , California