Word: dna
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Dates: during 1990-1999
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...modern disease. Some of our apelike ancestors undoubtedly suffered from it; so did the dinosaurs. In fact, says Robert Weinberg, a molecular biologist at the Massachusetts Institute of Technology, "it is a risk all multicellular organisms run." Each time a human cell divides, it must replicate its DNA, a biochemical manuscript some 3 billion characters long. In the course of transcribing such a lengthy document, even a skilled typist could be expected to make mistakes, and cells, like typists, occasionally err. More often than not, the mistakes they make are minor and quickly repaired by proteins that serve as miniature...
...conceptual revolution that is just now sweeping into the clinic began in the 1960s, when researchers started to realize that cancer is a disease of DNA, the master molecule that encodes the genetic script of life. One of DNA's most important jobs is to govern cell division, the process by which a cell makes a copy of itself and splits in two. Ordinarily, cell division is tightly regulated, but a cancer cell divides uncontrollably, pushing into surrounding tissue...
...genes and one oncogene. The first mutation spurs the growth of the cell, triggering the formation of a benign polyp. Later changes cause the polyp to expand and become increasingly irregular in shape. By the time a cell in this growing mass suffers a final, fateful hit to its DNA, many decades may have gone...
...cancer known to afflict particular families. These genes are carried by as many as 1 in every 200 Americans, making them the most common cause of cancer susceptibility yet discovered. In their normal form, these biological versions of computerized spelling checkers produce proteins that scoot along strands of replicating DNA, searching for tiny typos. When a protein finds an error in one of the words spelled out by DNA's four-letter chemical alphabet, it flashes an alarm. A person born with only one good copy of any of these genes is fine, until some cell...
Cancer-causing mutations can occur quite by accident. But chronic exposure to carcinogens -- chemicals whose by-products bind to DNA and damage it -- greatly accelerate the rate at which dividing cells make errors. Proven carcinogens include asbestos, benzene and some ingredients of cigarette smoke. Many carcinogens, it turns out, are not blunderbusses but leave highly individualized fingerprints in the DNA they touch. At the National Cancer Institute, Dr. Curtis Harris, a molecular epidemiologist, has been examining cells from liver- and lung-cancer patients, searching for mutations in a tumor-suppressor gene known as p53 (p stands for the protein...