题目内容
Genetic Engineering
Genetic engineering began when the DNA molecule (分子), the most basic unit of life, was first described in 1953 by James Watson and Francis Crick. An understanding of DNA led to the altering of normal cell reproduction. Experiments with altering human cells began in 1970. In one of the first ex- periments, patients were injected with a virus that would produce a life-saving enzyme, but their bodies would not accept it. In 1980 patients with a rare but fatal blood disease were injected with a pu- rified gene that was cloned through DNA technology. Another failure.
Genetic engineering got a legal boost (激励) in 1980. The U. S. Supreme Court said that a patent could be granted on a genetically engineered "oil-eating" bacterium (细菌). This bacterium would help clean up oil spills. The ruling encouraged companies to invent new life forms, and three important medical products were quickly developed.
Human interferon (干扰素)-a possible solution to some cancers and viral disease A newly engineered bac-terium produced hurnan interferon as a by-product. This new product reduced the cost of interferon.
Human growth hormone-for children whose bodies do not grow to normal height. An expensive growth hormone (荷尔蒙) was previously produced from human cadavers, but by changing the genetic make-up of the single-cell bacterium E. coli, and affordable growth hormone could be produced.
Human insulin (胰岛素)-for the treatment of diabetes. People with diabetes used to rely on a beef-or pork-based product until 1982. Now insulin can be manufactured by genetically altered bacteria.
Advances in genetic engineering have continued, though they constantly must be weighted against the safety of procedures. There is clearly much more to discover.
This passage is mainly about
查看答案
搜索结果不匹配？点我反馈
更多问题
在单相桥式整流电路中，若有一只整流管接反，则______。
The World's Best-Selling Medicine
Since ancient times, people all over the world have used willow to stop pain. The willow tree con-tains salicylic acid c水杨酸). This stops pain, but there is one problem. Salicylic acid also hurts the stomach. In 1853, a French scientist made a mixture from willow that did not hurt the stomach. How-ever, his mixture was difficult to make, and he did not try to produce or sell it.
In 1897, in Germany, Felix Hoffmann also made a mixture with salicylic acid. He tried it himself first and then gave it to his father because his father was old and in a lot of pain. His father's pain went away. and the mixture did not hurt his stomach.
Hoffmann worked for Bayer, a German company. He showed his new drug to his manager, who tested the drug and found that it worked well. Bayer decided to make the drug. They called it aspirin and put the Bayer name on every pill.
Aspirin was an immediate success. Almost everyone has pain of some kind, so aspirin answered a true need. Aspirin was cheap, easy to take, and effective. It also lowered fevers. Aspirin was a wonder drug.
At first, Bayer sold the drug through doctors, who then sold it to their patients. In 1915, the company started to sell aspirin in drugstores. In the United States, Bayer had a patent (专利权) on the drug. Other companies could make similar products and sell them in other countries, but only bayer could make and sell aspirin in the United States. In time, Bayer could no Ionger own the name aspirin in the United States. Other companies could make it there, too. However, Bayer aspirin was the most well known, and for many years, it was the market leader.
By the 1950s, new painkillers were on the market. Aspirin was no longer the only way to treat pain and reduce fever. Bayer and other companies looked for other drugs to make. However, in the 1970s they got a surprise. Doctors noticed that patients who were taking aspirin had fewer heart at-tacks than other people. A British researcher named John Vane found the reason aspirin helped to pre-vent heart attacks. In 1982, he won the Nobel prize for his research. Doctors started to tell some of their patients to take aspirin every day to prevent heart attacks. It has made life better for the many people who take it. It has also made a lot of money for companies like Bayer that produce and sell it !
Why didn't the French scientist continue to make the medicine that stopped pain？
在投资实践中，投资者按“宏观经济和证券市场运行状况——行业前景——公司经营状况”先后顺序的分析，被称为自上而下的分析。（）
分别判断图T8.4所示各电路是否满足正弦波振荡的相位条件。
微信支付 
支付宝支付