Three American Scientists Share Nobel Prize In Medicine

BALTIMORE - OCTOBER 05: Professor Carol Greider talks about the implications of her discovery during a news conference where she talked about winning the 2009 Nobel Prize in Physiology or Medicine at Johns Hopkins University October 5, 2009 in Baltimore, Maryland. Greider, 48, was recognized by the Royal Swedish Academy of Sciences for her 1984 discovery of telomerase, an enzyme that maintains the length and intergrity of chromosome ends and is critical for the health and survivial of all living cells and organisms. Greider, the Daniel Nathans Professor and Director of Molecular Biology and Genetics in the Johns Hopkins Institute for Basic Biomedical Sciences, shares the prize with Professor Elizabeth Blackburn of the University of California and Jacks Szostack of Harvard Medical School. (Photo by Chip Somodevilla/Getty Images)