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Input: Three Americans â Jeffrey C. Hall   Michael Rosbash and Michael W. Young â  have won the 2017 Nobel Prize in physiology or medicine for  their  work on molecular mechanisms that control circadian systems.
Hall was born in New York  Rosbash in Kansas City  and they both worked at Brandeis University.  Michael Young  was born in Miami and worked at Rockefeller University.
Jonathan Nackstrand / AFP/Getty Images Winners of the 2017 Nobel Prize in Physiology or Medicine Jeffrey C. Hall   Michael Rosbash and Michael W. Young  are pictured on a display during a press conference at the Karolinska Institute in Stockholm on Oct. 2  2017. Winners of the 2017 Nobel Prize in Physiology or Medicine Jeffrey C. Hall   Michael Rosbash and Michael W. Young  are pictured on a display during a press conference at the Karolinska Institute in Stockholm on Oct. 2  2017. (Jonathan Nackstrand / AFP/Getty Images) (Jonathan Nackstrand / AFP/Getty Images)
The trio's early work took place in 1984 when Hall and Rosbash worked together at Brandeis and  Young  at Rockefeller University to isolate the "period" gene  which controls the circadian rhythm of fruit flies. Hall and Rosbash then showed that the level of the protein encoded by this gene changes in a 24-hour cycle  going up during the day and down at night. They theorized that this protein blocked the activity of the period gene.

Nobel in physiology medicine awarded to 3 Americans for discovery of 'clock genes'