Since the early 1980s, scientists have revealed some 40 human genes involved in cancer. These 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 hag 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 insectic
A. harmful to the human body
B. necessary to the human body
C. the elements that form cancer
D. useless to the human body
Some houses are designed to be smart. Others have smart designs. An example of the second type of house won an Award of Excellence from the American Institute of Architects.
Located on the shore of Sullivan’s Island off the coast of South Carolina, the award-winning cube-shaped beach house was built to replace one smashed to pieces by Hurricane (飓风) Hugo 10 years ago. In September 1989, Hugo struck South Carolina, killing 18 people and damaging or destroying 36,000 homes in the state.
Before Hugo, many new houses built along South Carolina’s shoreline were poorly constructed, and enforcement of building codes wasn’t strict, according to architect Ray Huff, who created the cleverly-designed beach house. In Hugo’s wake, all new shoreline houses are required to meet stricter, better-enforced codes. The new beach house on Sullivan’s Island should be able to withstand a Category 3 hurricane with peak winds of 179 to 209 kilometers per hour
A. withstand peak winds of about 200 km / hr
B. anchor stronger pilings deep in the sand
C. break huge sea waves into smaller ones
D. prevent water from rushing into the house
Imagine eating everything delicious you want with none of the fat. That would be great, wouldn’t it
New "fake fat" products appeared on store shelves in the United States recently, but not everyone is happy about it. Makers of the products, which contain a compound called olestra, say food manufacturers can now eliminate fat from certain foods. Critics, however, say the new compound can rob the body of essential vitamins and nutrients and also cause unpleasant side effects in some people. So it’s up to consumers to decide whether the new fat-free products taste good enough to keep eating.
Chemists discovered olestra in the late 1960s, when they were searching for a fat that could be digested by infants more easily. Instead of finding the desired fat, the researchers created a fat that can’t be digested at all.
Normally, special chemicals in the intestines (肠道) "grab" molecules of regular fat and break them down so they
A. It may increase the risk of cancer.
B. It may impair the digestive system.
C. It may spoil the consumers’ appetite.
D. It may affect the overall fat intake.
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