2. 外语
  3. Founder mutations are a class of disease-causing genetic mutations, each derived from its own ancestral “founder" in whom the mu

Founder mutations are a class of disease-causing genetic mutations, each derived from its own ancestral “founder" in whom the mu

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问题     Founder mutations are a class of disease-causing genetic mutations, each derived from its own ancestral “founder" in whom the mutation originated. While most disease-causing mutations are found in humans at a rate of one in a few thousand to one in a few million people, founder mutation can occur at much higher rates. This apparent anomaly is partially explained by the fact that most founder mutations are recessive: only a person with copies of the affected gene from both parents becomes ill. Most people with only one copy of the gene—"carriers"—survive and pass the gene to offspring. Furthermore, the single copy of a founder mutation often confers a survival advantage on carriers. For example, the hereditary hemochromatosis mutation protects carriers from iron-deficiency anemia because the mutated gene allows increased efficiency of iron absorption.
The author of the passage mentions the "hereditary hemochromatosis mutation" primarily in order to illustrate
选项 A、the circumstances under which a founder mutation fails to cause a disease.
B、how difficult it is to predict the effects of founder mutations on carriers.
C、the difference between harmful founder mutation and those that are beneficial
D、how a single copy of a founder mutation can benefit a carrier.
E、a challenge to a particular theory about the transmission of founder mutations.
答案D
解析 本题属于功能题，定位句3s版本便是携带创始者突变基因会带来好处，因此选项D正确。A项创始者突变没能导致疾病的条件应该是只有一条基因被继承。B项文中没有提及困难。C项两种突变不符。都是一种创始者突变，有时候带来坏处，有时候带来好处。E项文中未提及。
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本试题收录于： GRE VERBAL题库GRE分类
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