Wake Up,Sleep Gene 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 bad-tempered.I have trouble remembering things.And all I want to do is crawl back into bed and sleep. How do you feel after you've stayed up late to finish schoolwork? Or the day after an overnight party? Scientists now say that your answers to these questions may depend on your genes. New research suggests that a gene called period 3 affects how well you function without sleep.The period 3 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 from the University of Surrey in England studied 24 people who had either two short or two long copies of period 3.Study participants had to stay awake for 40 hours straight.Then,they took tests that measured how quickly they pushed a button when number flashed on a screen and how well they could remember lists of numbers. Results showed that the people with the short form of period 3 performed much better on these tests than the people with the long form did.In both groups,people performed worst in the early morning.That's the time when truck drivers and other night-shift workers say they have the most trouble concentrating. 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. People with the long period 3 genes,by contrast,fell asleep in just 8 minutes.They also spent more time in dip sleep.That suggests that people with the long form of the gene need more and deeper sleep to keep their brains working at top form. I think I must have the long form of period 3.What about you? If one lacks enough sleep,one should avoid doing important or dangerous things  _  .
at noon at night in the afternoon at dawn