Word: dna
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Dates: during 1990-1999
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...gene therapy, most of the current "smart bombs," as in the case of Ashanthi DeSilva, are viruses, which by their nature invade cells and deposit their genetic material into the cell nucleus. Researchers have learned how to strip the viruses of their reproductive genes, insert into the viral DNA the beneficial gene they want to deliver, and then let the virus infect a patient's cells. The virus inserts its own now harmless genes, as well as the beneficial one, into the cellular DNA. If all goes well and the gene "expresses" itself, the cell begins producing the needed protein...
...problem is that the altered viruses do not always seek out the target cells and sometimes insert themselves in the wrong place in the cellular DNA. Then too, once in place, the new genes sometimes fail to express themselves. "There are still a few walls to get over," Anderson concedes. He points out that in the initial trial, viruses used for cystic fibrosis, for example, produced an inflammatory response: "So the trials were halted, and another generation of viral vectors was developed. Now we're going to restart the clinical trials with these new-generation vectors," which he thinks will...
...time, a single abnormal cell becomes two, then four, then eight, then 16. Early on, these cells develop a repertoire of "tricks" that confer a survival advantage. Among other things, the tricks ensure that mutation will pile on mutation by shucking off, or silencing, genes that ordinarily monitor replicating DNA for chemical errors. The malignant cells quickly become resistant to the poisons physicians prescribe to kill them. They also acquire the disturbing ability to stimulate the formation of nutrient-bearing blood vessels, thus spurring their own growth. Even if malignant cells grow rather slowly, they grow inexorably, eventually forming...
...cell divides, normally or otherwise, it does so not all at once but in a series of carefully orchestrated steps. Each step provides oncologists with an opportunity to intervene in the process. In order to complete a successful division, for example, a cell must first faithfully copy its DNA. If a cell makes mistakes in this critical task, vigilant enzymes quickly call a halt to the process until repairs can be made. Sometimes, however, the DNA of a dividing cell is too badly damaged to be salvaged. At this point, these same enzymes help activate a kamikaze circuit that compels...
Virtually all anticancer drugs interfere with cell division in some fashion. Cyclophosphamide, the compound that finally banished Dustin Fagan's cancer, belongs to a broad class of drugs that damage the DNA molecule by plastering it with sticky cross-links, thus triggering the suicide sequence. By contrast, the taxoids--including taxol, the compound isolated from the bark of the yew tree that was approved by the Food and Drug Administration as a weapon against ovarian cancer in 1992--cause the same suicidal result by deactivating a molecular machine that, just before cell division, separates the DNA in each chromosome into...