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Bloodletting and vitamin pills are the future for astronaut health regimes. So hints a provocative proposal on the benefits of p

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问题     Bloodletting and vitamin pills are the future for astronaut health regimes. So hints a provocative proposal on the benefits of personalized gene-based medicine for space travelers.
    Humans in space are at risk of a variety of ailments, from brittle bones caused by low gravity to cancer triggered by cosmic radiation. Astronauts on the International Space Station(ISS)already take supplements to counteract ill effects, such as vitamin D for bone strength.
    But when traveling further into space, such as to an asteroid or Mars, astronauts will be exposed to radiation doses close to NASA’s acceptable lifetime limits, upping their chances of developing illnesses from damaged DNA.
    To reduce each individual’s risk, we should examine their genome and then design countermeasures to protect against any potential problems, say Michael Schmidt of MetaboLogics in Fort Collins, Colorado, and Thomas Goodwin of NASA’s Johnson Space Center in Houston, Texas.
    The aim is not to weed out astronauts with deficiencies, but to ensure those who fly are in the best possible condition before they go to space, says Schmidt.
    For example, certain gene mutations are known to reduce the stability of DNA, and this effect is amplified by a lack of folate. A person with the mutation could take folate supplements to protect against an increased risk of genetic damage from radiation exposure.
    Reduced folate levels have also been linked to vision problems experienced by roughly a quarter of astronauts returning from the ISS. It is not yet clear whether the eye problems have a genetic component, but that is the kind of thing more focused research could reveal, says Schmidt.
    Even a simple treatment like preflight bloodletting could prove useful when combined with genetic analysis, the pair say. People with a genetic mutation to build up iron in their bodies are at greater risk of radiation damage in space. An older male astronaut with the mutation will have built up high concentrations of iron over his lifetime(women are less at risk because they lose iron during menstruation). Bloodletting, along with an iron-restricted diet, could be an effective way to reduce this risk.
    Genetic profiles can also help inform the types of drugs astronauts take into space, says Graham Scott of Baylor College of Medicine in Houston. He is looking at personalized medicine for Inspiration Mars, a private venture which plans to send humans on a fly-by of the Red Planet in 2018.
    Roughly half of astronauts have experienced back pain during missions, which is treated in space with exercise and painkillers. But people with variants of the liver gene CYP2D6 can metabolize(新陈代谢)drugs such as the painkiller codeine too quickly, potentially leading to an overdose—and there is no hospital en route to Mars. Instead, if an astronaut is known to have this mutation they can be given a lower dose or an alternative treatment.
    Jasper Rine of the University of California, Berkeley, says Schmidt and Goodwin’s proposal makes sense in principle, but we don’t yet know enough about gene variations to predict which astronauts will have gene-based health problems. And in the immediate future, he thinks deep-space pioneers will have bigger things to worry about. "Those with the courage to ride into space on a rocket built by the low bidder on a government contract face a wide range of risks," says Rine.
From the passage, we get to know that astronauts are at greater risk of radiation damage______.
选项 A、if they have less iron concentration
B、if they have more folate supplements
C、if they have no gene variations
D、if they have flown further into the space
答案D
解析 推断题。根据第三段可知，当航天员飞到太空中更远的地方，比如飞到一颗小行星或火星上，就会受到很大辐射，造成基因受损并增大患病风险，故选[D]。
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