Greider, Carol Widney (1961-…), an American biologist, shared the 2009 Nobel Prize in physiology or medicine for her work with telomeres. Telomeres are protective structures on the ends of chromosomes, threadlike parts in cells that carry genetic (hereditary) information (see Telomere ). Greider shared the prize with two other American biologists, Australian-born Elizabeth H. Blackburn and English-born Jack W. Szostak.
Chromosomes carry genes, which are encoded in the structure of a chainlike molecule called DNA (deoxyribonucleic acid). Genes are the chemical instructions that determine the form and function of each cell in an organism. A telomere includes a particular highly repetitive sequence of DNA at the chromosome’s end. Together with specialized proteins, this sequence forms a protective “cap” on the chromosome—the telomere. However, the enzyme (substance that speeds up chemical reactions in living things) that duplicates DNA cannot copy all the way to the end of a strand. For this reason, each time the entire chromosome is duplicated during cell division, a bit of DNA is lost from the end of the telomere.
As a graduate student in Blackburn’s laboratory, Greider studied how telomeres form on the end of chromosomes. In 1984, she discovered that an enzyme was necessary for the formation of telomeres. She and Blackburn called the newly discovered enzyme telomerase. Telomerase extends the telomere by adding new repetitive units of DNA to its end. This lengthening compensates for the loss of DNA that usually occurs during cell division. However, many cells—including most cell types in the human body—do not have sufficient telomerase to completely counteract the shortening of telomeres. Thus, scientists have observed that telomeres tend to shorten as individuals age. Scientists believe that the shortening of telomeres plays an important role in cancer and in other diseases associated with aging.
Greider was born on April 15, 1961, in San Diego. She graduated from the University of California at Santa Barbara in 1983. She began graduate research in molecular biology with Blackburn at the University of California at Berkeley, where Greider earned her Ph.D. degree in 1987. She then conducted research at the Cold Spring Harbor Laboratory in Long Island, New York. In 1997, she joined the faculty at Johns Hopkins University in Baltimore, where she became director of the Department of Molecular Biology and Genetics.
See also Blackburn, Elizabeth Helen ; Szostak, Jack William .
