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  3. About half of all medical patients get a drug, in any given year, that could interact with their genes and cause serious side ef

About half of all medical patients get a drug, in any given year, that could interact with their genes and cause serious side ef

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问题     About half of all medical patients get a drug, in any given year, that could interact with their genes and cause serious side effects. Inexpensive gene tests, as yet only available in a few hospitals, could avoid these life-threatening problems.
    Tailoring treatments to genetic makeup is part of the futuristic vision of personalized medicine, where all care is custom-fit to an individual’s DNA.【B11】____________Although total human  genome sequencing costs $1,000, getting drug-gene results on a few hundred genes at St. Jude costs about half that much for each patient. "The era of precision medicine is upon us," says Dan Roden, assistant vice chancellor for personalized medicine at Vanderbilt University Medical Center. "The low-hanging fruit here is pharmacogenomics."
    Unfortunately this fruit is being plucked by only a handful of hospitals.【B12】___________The sad result, advocates say, is that people are getting sick needlessly. Between 5 and 30 percent of the global population is estimated to have the same troublesome gene variant and it affects how well people respond to multiple medications, not just voriconazole. Roughly 50 percent of hospital patients get a drug in any one-year period that could cause serious side effects because of that person’s genetic makeup, according to analyses from St. Jude and Vanderbilt.
    Doctors are not accustomed to making medication choices using genetics.【B13】_______________
    If clinicians would consider genetics, here is what they could learn about prescribing the common painkiller codeine. Typically the body produces an enzyme called CYP2D6 that breaks down the drug in-to its active ingredient, morphine, which provides pain relief. Yet as many as 10 percent of patients have genetic variants that produce too little of the enzyme, so almost no codeine gets turned into morphine. These people get little or no help for their pain. About 2 percent of the population has the reverse problem.【B14】______________________
    These types of drug-gene interactions explain some long-standing medical mysteries. As early as 510 B.C. Greek mathematician Pythagoras found that when some people ate a particular type of bean they would get hemolytic anemia, a potentially deadly condition in which red blood cells are destroyed and removed from the bloodstream.【B15】____________________That very same genetic variant—which can be spotted with to-day’s gene tests—also predisposes patients to hemolytic anemia if they take several drugs now on the market, including rasburicase, a medication often given to patients with leukemia
    [A]   Thousands of years later, researchers conclude that many such drug-gene interactions—both severe and subtle—could be avoided by taking different doses of the drugs or turning to substitutes.
    [B]   They have too many copies of the gene that produces the enzyme, leading to overproduction. For them, a little codeine can quickly turn into too much morphine, which can lead to a fatal overdose.
    [C]   Another big obstacle to wider use of the test is the lack of a prescribing road map. Many doctors were educated in an era before such testing was available so they do not even think to order them.
    [D]   Remarkably, part of that vision—genetic drug matching, called pharmacogenomics—is already turned into reality in St. Jude Children’s Research Hospital. The hospital tests patients for some genes that affect which drugs—and what doses—would work best in their body.
    [E]  Lack of insurance coverage for the tests, along with confusion among doctors about what to do with the genetic data, is preventing the exams from being widely used.
    [F]   Now researchers discovered why that reaction occurred: these people inherit genetic variants that lead to a deficiency in the production of an enzyme called glucose-6-phosphate dehydrogenase (G6PD), which normally prevents red blood cell destruction.
    [G]  What they have done, for decades, is to look at easily observed factors such as a patient’s age and weight and kidney or liver functions. They also considered what other medications a patient is taking and any personal preferences.
【B15】
选项
答案F
解析 空格前提到公元前510年毕达哥拉斯发现有些人食用某种豆之后就会得溶血性贫血症。空格后指出，如今有着这一突变基因的人要是服用了某些药物也会得溶血性贫血症。空格前后谈论的都是溶血性贫血症，因此空格处也应该与此相关。F的关键词red blood cell destruction对应空格前的red blood cells are destroyed；而红血球遭到破坏是导致溶血性贫血症的原因，这说明F谈论的也是溶血性贫血症的问题，与空格前后的话题一致。从内容上看，F解释了溶血性贫血症发病的原因，与空格前的内容构成顺承关系；其中，that，reaction指代空格前说的现象，而genetic variants that…destruction则对应空格后的That very same genetic variant。故本题选F。
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