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Người theo dõi (5)

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HH

Mark the letter A, B, C or D on your answer to indicate the correct answer to each of the question from 1 to 10.

The first two decades of this century were dominated by the microbe hunters. These hunters had tracked down one after another of the microbes responsible for the most dreaded scourges of many centuries: tuberculosis, cholera, diphtheria. But there remained some terrible diseases for which no microbe could be incriminated: scurvy, pellagra, rickets, beriberi. Then it was discovered that these diseases were Câused by the lack of vitamins, a trace substance in the diet. The diseases could be prevented or cured by consuming foods that contained the vitamins. And so in the decades of the 1920‟s and 1930‟s, nutrition became a science and the vitamin hunters replaced the microbe hunters.

In the 1940‟s and 1950‟s, biochemists strived to learn why each of the vitamins was essential for health. They discovered that key enzymes in metabolism depend on one or another of the vitamins as coenzymes to perform the chemistry that provides cells with energy for growth and function. Now, these enzyme hunters occupied center stage.

You are aware that the enzymes hunters have been replaced by a new breed of hunters who are tracking genes – the blueprints for each of the enzymes – and are discovering the defective genes that Câuse inherited diseases – diabetes, cystic fibrosis. These gene hunters, or genetic engineers, use recombinant DNA technology to identify and clone genes and introduce them into bacterial cells and plants to create factories for the massive production of hormones and vaccines for medicine and for better crops for agriculture. Biotechnology has become a multibillion-dollar industry.

In view of the inexorable progress in science, we can expect that the gene hunters will be replaced in the spotlight. When and by whom? Which kind of hunter will dominate the scene in the last decade of our century and in the early decades of the next? I wonder whether the hunters who will occupy the spotlight will be neurobiologists who apply the techniques of the enzyme and gene hunters to the functions of the brain. What to call them? The head hunters. I will return to them later.

In the third paragraph, the author compares cells that have been genetically altered by biotechnicians to ___________ 

A. gardens 

B. factories 

C. hunters 

D. spotlights

HH

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

Why is it that flying to New York from London will leave you feeling less tired than flying to London from New York? The answer may be a clear case of biology not being able to keep up with technology. Deep inside the brain there is a “clock” that governs every aspect of the body’s functioning: sleep and wake cycles, levels of alertness, performance, mood, hormone levels, digestion, body temperature and so on. It regulates all of these functions on a 24-hour basis and is called the circadian clock (from the Latin, circa “about” + dies “day”).

This body clock programmes us to be sleepy twice a day, between 3-5 a.m. and again between 3-5 p.m. Afternoon tea and siesta times are all cultural responses to our natural biological sleepiness in the afternoon. One of the major causes of the travelers’ malady known as jet lag is the nonalignment of a person’s internal body clock with clocks in the external world. Crossing different time zones confuses the circadian clock, which then has to adjust to the new time and patterns of light and activity. To make matters more complex, not all internal body functions adjust at the same rate. So your sleep or wake may adjust to a new time zone at one rate, while your temperature adjusts at a different pace. Your digestion may be on a different schedule altogether.

Though we live in a 24-hour day, the natural tendency of the body clock is to extend our day beyond 24 hours. It is contrary to our biological programming to shrink our day. That is why travelling in a westward direction is more body-clock friendly than flying east. NASA studies of long haul pilots showed that westward travel was associated with significantly better sleep quantity and quality than eastward flights. When flying west, you are “extending” your day, thus travelling in the natural direction of your internal clock. Flying eastward will involve “shrinking” or reducing your day and is in direct opposition to your internal clock’s natural tendency.

One of the more common complaints of travelers is that their sleep becomes disrupted. There are many reasons for this: Changing time zones and schedules, changing light and activity levels, trying to sleep when your body clock is programmed to be awake, disruption of the internal circadian clock and working longer hours. Sleep loss, jet lag and fatigue can seriously affect our ability to function well. Judgment and decision-making can be reduced by 50%, attention by 75 percent, memory by 20 percent and communication by 30 percent. It is often suggested that you adjust your watch as soon as you board a plane, supposedly to try to help you adjust to your destination’s schedule as soon as you arrive. But it can take the body clock several days to several weeks to fully adjust to a new time zone.

According to the passage, which of the following is TRUE about “jet lag”?

A. It makes our body clock operate badly. 

B. It extends the hours of our body clock.

C. It causes our body clock to change. 

D. It upsets our body’s rhythms.