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Some people can stay up all night and still get work done the next day. I’m not one of them. After a night without enough sleep, I feel sleepy. I have trouble remembering things. And all I want to do is to go back to bed and sleep.

How do you feel after you’ve stayed up late to finish schoolwork? Or the day after a slumber(睡眠) party? Scientists now say that your answers to these questions may depend on your genes, which tell our bodies and brains what to do. People have about 40,000 genes, and each gene can have different forms.

A new research suggests that a gene called period3 affects how well you function without sleep. The discovery adds to older evidence that period3 helps determine whether you like to stay up late or get up early.

The period3 gene comes in two forms: short and long. Everyone has two copies of the gene. So, you may have two longs, two shorts, or one of each. Your particular combination depends on what your parents passed on to you.

Scientists studied 24 people who had to stay awake for 40 hours straight. Then they took tests that measured how well they could remember lists of numbers.

Results showed that the people with the short form of period3 performed much better than those with the long form did. In both groups, people performed worst in the early morning. After the first round of experiments, participants were finally allowed to sleep. People in the group that performed well on the tests took about 18 minutes to nod off(瞌睡).

People with long period3 gene fell asleep in just 8 minutes. They also spent more time on deep sleep. That suggests that people with the long form of the gene need more and deeper sleep to keep their brains working in top form.

I think I must have the long form period3. What about you?

68. The purpose of the writer in the first paragraph is to ____________.

   A. attract readers to the topic of the passage

   B. show his /her poor memory for things

   C. show his /her envy of those energetic people

   D. prove his/her need for sleep

69. Whether you can stay up or not depends on___________.

   A. the size of your brain         B. the kind of genes you have

   C. your health                 D. your will

70. The aim of the research is to _______.

   A. find a new gene called period3   B. find out how genes affect a person’s need for sleep

   C. test how long you can stay awake   D. measure how good your memory is