单选题 Don"t hate those people who are perky (精力充沛的) and efficient after only a few hours of sleep. They can"t help it. New research suggests that a genetic mutation (基因突变) may explain why some people sleep less.
In 2001, geneticist Ying-Hui Fu and colleagues identified a mutation in a gene called Per2 that appeared to cause Familial Advanced Sleep-Phase Syndrome (FASPS). People who have this condition sleep a normal 8 hours, but they go to bed earlier than most people, retiring at 6 or 7 in the evening and waking at 3 or 4 in the morning. "After that was published, a lot of these people with unusual sleep schedules came to us," says Fu, who is now at the University of California, San Francisco. "So we started to collect DNA samples." The team now has genetic information from more than 60 families.
Fu and her colleagues have spent the past several years mining this vast genetic storehouse for more mutations that might affect sleep patterns. In 2005, they uncovered another mutation associated with FASPS. And now they say they have found the first genetic mutation in humans that appears to affect sleep duration rather than sleep timing. The mutation lies in DEC2, a gene that codes for a protein that helps turn off expression of other genes, including some that control circadian rhythm (生理节律), the internal clock (生物钟) that regulates a person"s sleep-wake cycle. The mutation occurred in just two people, a mother and her daughter. The women sleep an average of only 6.25 hours, whereas the rest of the family members sleep a more typical 8 hours.
To confirm that this mutation shortens sleep, Fu and colleagues engineered mice to carry the mutant form of DEC2. The mutant mice slept about an hour less than normal mice, the team reports on 13 August in Science. The finding also held for fruit flies: Mutant flies slept about 2 hours less than normal flies.
DEC2 likely isn"t the whole story when it comes to short sleep. "Genetic control of sleep is going to be complex and is going to include multiple types of genes," says Shaw, who was not affiliated with (与......有关系) the study. But that doesn"t diminish the importance of this paper, he notes. "It"s really an amazing piece of work."
"The findings", says Fu, "could lead to better treatments for sleep disorders". If the mutated form of DEC2 were available in a pill, Fu says she"d take it, noting that she needs about 8 hours of shuteye a night to feel rested. "All my life I"ve wanted to be able to sleep less."

单选题 Which of the following is true about the mutation in Per2 mentioned in the second paragraph?

【正确答案】 D

【答案解析】[解析] 根据题干将本题出处定位于第2段。
文章第2段开头提到了遗传学家傅英惠和同事们发现：在被称为Per2的一个基因上的突变似乎可以导致家族性睡眠时段超前综合征(FASPS)。患有这种症状的人也是睡8个小时，但是，他们比大多数人要早睡几个小时。由此可见，Per2基因突变会导致人早睡，D中的sleep earlier对应文中的go to bed earlier。由文中提到的“患有这种症状的人也是睡8个小时”可排除A和C；B属于反向干扰，也予以排除。

单选题 According to the passage, the mutated DEC2 ______.

【正确答案】 A

【答案解析】[解析] 文中首次提到突变的DEC2基因是在第3段第4句，故将本题出处定位于此。
第3段第4句提到突变的：DEC2基因，接着下一句说，这种突变只发生在一对母女身上，结合本段第1句可知，傅英惠和她的同事们是通过挖掘这个巨大的基因库，从而找到了突变的DEC2基因，再结合第2段倒数第三句可知，这个巨大的遗传信息库是由那些主动与傅英惠取得联系的睡眠时间不正常的人提供的。综上分析可知，突变的DEC2基因是由那些主动与傅英惠取得联系的睡眠时间不正常的人提供的。研究者先发现了Per2上的突变，后来才发现的DEC2上的突变，排除B；C是利用第3段第2句设置的干扰项，这里说的“和FASPS相关的突变”并不是指DEC2基因突变，故排除C；由第3段最后一句中提到的“这两位女性平均一天仅睡6.25小时，而她们的其他家庭成员都正常地睡8个小时”可排除D。

单选题 What is wrong with the mother and her daughter?

【正确答案】 D

【答案解析】[解析] 根据题干中的mother and her daughter将本题出处定位于第3段倒数第二句。
第3段倒数第二句提到一对母女身上发生了DEC2基因突变，前面具体讲述了这种基因突蔓的影响：这种基因突变可以影响睡眠时长。该基因编码的蛋白质可以关闭其他基因编码的表达，其中包括一些可以控制生理节律的基因——控制睡眠与清醒状态循环的生物钟。由该突变引起的症状(睡眠时间不是典型的8个小时)可推知，那些控制生理节律的基因被关闭的模式不是典型的8小时模式。其他三项都是对该句的错误理解。

单选题 Fu and colleagues changed flies" DEC2 ______.

单选题 What does Shaw think of DEC2?

【正确答案】 D

【答案解析】[解析] 根据题干中的Shaw将本题出处定位于第5段第2句。
第5段第2句指出没有参与研究的肖说，睡眠时间的基因控制是很复杂的，包含了多种基因；本句是对上一句的补充，即，肖认为DEC2并不能完全解释睡眠时间缩短的原因。A的说法不够准确，肖并没有完全否认DEC2与睡眠时间缩短之间的联系；B属于反向干扰，可排除；文中说的是控制睡眠时间的基因有很多种，而非DEC2有很多种基因，故C也可排除。