"This groundbreaking work spanning genetics and biochemistry has laid the basis for much of our understanding of modern pharmacology as well as how cells in different parts of living organisms can react differently to external stimulation, such as light and smell, or the internal systems which control our bodies such as hormones," Downs said in a statement.
The U.S. has dominated the Nobel chemistry prize in recent years, with American scientists being included among the winners of 17 of the past 20 awards.
This year's Nobel announcements started Monday with the medicine prize going to stem cell pioneers John Gurdon of Britain and Japan's Shinya Yamanaka. Frenchman Serge Haroche and American David Wineland won the physics prize Tuesday for work on quantum particles.
The Nobel Prizes were established in the will of 19th-century Swedish industrialist Alfred Nobel, the inventor of dynamite. The awards are always handed out on Dec. 10, the anniversary of Nobel's death in 1896.
AP Science Writer Malcolm Ritter in New York and AP writers Amanda Kwan in Phoenix, Jack Jones in Columbia, South Carolina, and Danica Kirka in London contributed to this report.
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