2. 外语
  3. During the Second World War, doctors tried to save severely burned pilots with grafts of donated skin. The grafted skin looked g

During the Second World War, doctors tried to save severely burned pilots with grafts of donated skin. The grafted skin looked g

admin2017-11-08  49
问题    During the Second World War, doctors tried to save severely burned pilots with grafts of donated skin. The grafted skin looked good for a few days, but then withered and died. Studies led by Peter Medawar—who won a 1960 Nobel Prize for his work—found that grafts of an individuals own skin did work, while those of a donor did not. We now know that the donor skin grafts failed because the recipient’s immune system recognized the grafted skin as foreign and killed it. The same process leads to the rejection of donated organs. But how does our immune system learn what is self and what is foreign?
   As immunologist Daniel Davis explains in The Compatibility Gene, it is all down to specific genes—formally known as the major histocompatibility complex genes. Although our appearance, lifestyle and career path may make us feel unique, we are actually always one of a group: it is only our compatibility genes that define us as true individuals. Davis provides a well-written and easy-to-read account of the sometimes complicated biology behind the crucial genes that affect our lives so profoundly.
   From early on in the evolution of life, individual cells—and later multicellular organisms— developed the ability to recognize that which was the same as them, and that which was different. Davis recounts how, when we are growing as fetuses, our compatibility genes train the immune system to recognize our own cells and tissues as "self" and so, in healthy people, they know what not to attack. Our cells are identified by the presence of unique surface molecules, coded for by the compatibility genes.
   Meanwhile, our immune systems make antibodies. These are randomly generated in a kind of lottery, which means they will be able to attack a great diversity of molecules, especially those of pathogens. By chance, though, a few of these antibodies will also match the compatibility-gene molecules on our own cells. Leaving such antibodies around would be suicide—literally. To stop this, Darwinian-style selection comes into play within the immune system, eliminating any cells that produce antibodies matching "self".
Why does the author say "Although our appearance, lifestyle and career path may make us feel unique, we are actually always one of a group"?
选项 A、People may have same appearance, lifestyle or career path, which can not be the unique feature.
B、Our appearance, lifestyle and career path can help us distinguish ourselves from a group.
C、People may have different appearance, lifestyle or career path, but they still can not be true individuals.
D、Our appearance, lifestyle and career path define us to be a member of a group.
答案C
解析 根据题干句子将该题定位至文章第二段。该句的意思是尽管我们的外表、生活方式和职业可能让我们觉得自己独一无二，可我们实际上总是一个群体中的一员：只有我们的亲和基因将我们定义为真正的独立个体。侧重点是冒号后的话，而题干中并未写明这句话。根据选项只有C更符合文章，C指出人们有着不同的外表、生活方式和职业道路，但仍然不能成为真正的个体(因为只有亲和基因才能决定人们是真正的个体)。所以选C。
转载请注明原文地址:https://kaotiyun.com/show/g1a7777K
0

大学英语四级

相关试题推荐
随机试题
最新回复(0)