Research on genes will ( ) exciting new medical treatments

cultural research drive since the 1920's, when hybrid corn was developed. Surprisingly, the new genetic revolution is not taking place in America's fields. Instead, it is occurring in biology laboratories, for it involves the deliberate manipulation in test tubes of the genes of crop plants. This genetic engineering may prove the biggest boon to agriculture since plant breeding began.

The new concepts grew out of the bioengineering of bacteria for the production of such things as human hormones and vaccines for viral diseases. Plant cells, however, are far more complex than bacteria, and it will probably take many years for today's encouraging laboratory results to have a major impact on the farm. In fact the payoff may not come until the next century.

But although bio-technologists are still in the earliest phases of this new field of science, they are already actively exploring ways to redesign plants so they will use sunlight mere efficiently, resist viruses and other pests, grow in hot or dry areas, in saline soils or in the presence of pesticides, and perhaps even make their own fertilizer out of nitrogen in the air. In addition, scientists have had early success in making wholly new plants that are unavailable by conventional plant breeding-a potato-tomato combination, for example.

The new technology holds the promise of virtually limitless horizons in food production. Only imagination sets the limits: frost-resistant wheat, tropical potatoes, saltwater rice, a plant producing a combination of a pea and a carrot-all may be with us one day.

Vaccines for viral diseases are often produced from ______.

A．plant cells

B．human hormones

C．crop plants

D．bacteria

Which of the following statements is true（).

A、The genes involved in cancer are all classed as oncogenes.

B、All genes involved in cancer are of a class called tumor suppressor genes.

C、Both oncogenes and tumor suppressor genes are involved in cancer.

D、No unifying classifications can be applied to the genes involved in cancer.

According to this passage ,the new generic revolution involves ______.

A．experiments on plants in the fields

B．developing strains of hybrid corn

C．breeding plants in test tubes

D．rearranging plant genes in laboratories

ese genes are essential for normal growth, but can be subverted to cause a tumor.

Dr. Jorge Yunis of the University of Minnesota Medical School in Minneapolis has found that 70 percent of oncogenes, or cancer-causing genes, are located near inherited weak points on chromosomes(染色体). Varying from individual to individual, vulnerable to chemical carcinogens(致癌剂), X rays and other cancer-inducing agents.

"If a chromosome snaps apart in the immediate vicinity of an oncogene," says Yunis, "normal genetic control mechanisms could break down and the stage would be set for the formation of cancer." Younis has shown that such a sequence occurs at the beginning of numerous leukemias (白血病), lymphomas(淋巴瘤) and some tumors of the lung, colon(结肠) and breast.

Yunis and other investigators have found that petroleum-based products--notably pesticides and insecticides-damage specific sites on at least two of the 23 pairs of human chromosomes that carry genetic information. Similarly, tobacco smoke tends to attack a part of another chromosome.

From paragraph 1, we know that some 40 genes involving in cancer are ______. ()

A．harmful to the human body

B．necessary to the human body

C．the elements that form. cancer

D．useless to the human body

B.F. Skinner______.

A．supports the nature theory.

B．thinks the environment plays an important role in determining character

C．believes instincts govern behavior

D．believes in the importance of genes in determining personality

A.WI文件表示表格

B.WI文件表示作业指导书

C.WI文件表示程序文件

D.WI文件表示质量手册

A.SOP

B.WI

C.SOP、WI

D.领导要求

A.车轮

B.方向盘

C.转动

D.批判

A.weekend

B.weekday

C.welcome