第三篇

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 experiments, 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 purified gene that was cloned through DNA technology. Another failure.

Genetic engineering got a legal boost(激勵) in 1980. The U.S. Supreme Court said that a patent could be granted on a genetically engineered "oil-eating" bacterium(細(xì)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.

l Human interferon(干擾素)-- a possible solution to some cancers and viral disease. A newly engineered bacterium produced human interferon as a by-product. This new product reduced the cost of interferon.

l Human growth hormone-- for children whose bodies do not grow to normal height. An expensive growth hormone(荷爾蒙) 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.

l Human insulin(胰島素)-- 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.

41. This passage is mainly about

A. the human growth hormone.

B. the effects of altering cells.

C. insulin resistance.

D. U.S. Supreme Court rulings.

42. Genetic enginerring may be defined as

A. the altering of normal cell reproduction

B. a branch of applied chemistry.

C. a procedure that holds little promise.

D. a study on life-saving enzymes.

43. According to the passage, human interferon

A. is a hormone that causes disease.

B. could be used to treat cancer.

C. is a viral disease

D. has been cured

44. In this passage, the three genetically engineered medical products are presented

A. as a process.

B. from earliest to latest.

C. in a simple list.

D.as a story.

45. In the last paragraph, the word "weighed" has the cloest meaning with

A. had great influence

B. became a burden.

C. measured accurately.

D. considered carefully.

本題分?jǐn)?shù)（15）

41  B  從第一段尤其是前三句中我們可以了解到，遺傳工程就是對細(xì)胞進(jìn)行改造，而后面

列舉的三種重要的醫(yī)療產(chǎn)品正是細(xì)胞改造的成果，因此B項可以概括短文的內(nèi)容，其他

三個選項均不恰當(dāng)。

42  A  本文介紹的是遺傳工程，第一段后半部說到，對DNA的了解導(dǎo)致了對正常細(xì)胞繁殖

的改造，并由此進(jìn)行了一些實驗，可見遺傳工程就是“對正常的細(xì)胞繁殖進(jìn)行改造”。

43  B  第三段第一句明確說到，“人體干擾素可能解決某些癌癥和病毒性疾病的問題”。

44  C  從文章的表達(dá)方式來看，可以很明顯看到，這三種通過遺傳工程產(chǎn)生的醫(yī)療產(chǎn)品是

以羅列的方式來介紹的，其他三個選項均不符合文章的實際內(nèi)容。

45  D  在本句中，作者說“遺傳工程還在繼續(xù)獲得進(jìn)展，不過還需認(rèn)真考慮它的安全性”

在這里weigh實際就是“衡量、考慮”的意思，其他三個選項均不恰當(dāng)。

（責(zé)任編輯：vstara）

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