| People have often wondered about Margaret Thatcher's famous claim that she only needed four hours of sleep a night. People were amazed that former British Prime Minister had managed to run the country on so little sleep. Most people need at least seven or eight hours rest every night. But now scientists have discovered a gene(基因)that affects the amount of sleep we need and which allows some people to survive on fewer hours. They found a mother and a daughter who have a rare gene that allows them to sleep less  than the rest of their family -but still feel alert during the day. The pair managed to stay alert on about six hours sleep a night, two hours less than the rest of their family needs. The finding, published in Science magazine, offers a new direction for studies on how sleep affects health. Experts say adults need seven to nine hours of sleep for good health, while teenagers and kids need more. People who don’t get enough sleep are more likely to get sick and suffer from memory loss. In 2001,scientists at the University of California discovered a mutation(突变)in a  gene that causes people with that gene to have very unusual sleeping patterns. These people go to bed around 7:30 pm and wake around 3:30 am. Now the team has found a gene that affects how long a person can stay asleep. In the family they studied, the 69-year-old mother and her 44-year-old daughter usually went to bed around 10 pm. The mother woke up around 4 am, and her daughter woke up around 4:30 am. Both of them felt fully rested. Blood tests showed the women have a mutation in a gene named DEC2, which regulates the body's clock. Researcher Ying-Hui Fu bred(培育) mice and fruit flies to carry the mutation. The flies and mice with the mutation slept less than ordinary flies and mice, and needed less time to recover from little sleep. |
| 1. What is the main idea of the passage? |
| A. Less sleep does not affect people's health. B. Different people have different sleeping patterns. C. New measures can reduce the effect of less sleep on health. D. The hours we need to sleep may be affected by some gene in our body. |
| 2. The underlined word "alert" in Paragraph 4 is similar in meaning to . |
| A. comfortable B. wide awake C. quite alive D. sleepy |
| 3. In the study, the mother and the daughter . |
| A. were found to have a mutation in the gene DEC2 B. were asked to sleep less than other family members C. had the same sleeping pattern as other family members D. suffered from memory loss for sleeping only six hours a night |
| 4. According to the passage, the new finding can help . |
| A. recover memory loss B. cure sleeping problems C. get rid of mice and fruit flies more easily D. explain why some people need less sleep to feel fully rested |