Elizabeth H. Blackburn, Carol W. Greider, and Jack W. Szostak won the 2009 Nobel Prize in Physiology or Medicine for their discovery of how chromosomes are protected by telomeres and the enzyme telomerase. Their research explained how telomeres prevent chromosome degradation during cell division, with important implications for aging and cancer research. The other options won in different years: Marshall and Warren (2005) for H. pylori, Capecchi, Evans, and Smithies (2007) for gene targeting, and Fire and Mello (2006) for RNA interference.