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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 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. According to the context, the word in "oncogenes" in para. 2 means()
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We first think of the traditional or nuclear family. This is a two-generation family, the father and the mother and their own children. Most couples wanted to have four children, two boys, two girls.Some nuclear families, however, may add one or more grandparents to come m live with them, that is three generations. This kind of family with grandparents, parents, and grandchildren is called an extended family. This family type was not very common during the later half of the twentieth century, but it’s becoming more common now as an elderly grandparent moves in to live with a son or daughter. This is more possible now that American homes have become larger. What is interesting, however, is that after the grandchildren move out of the home and start their own families, this extended family shrinks back to a nuclear family, with just two generations again living together, a grandparent and parents, with the grandchildren coming only for occasional visits.Now, the fatherless or motherless family is one kind of what we call a single-parent family. In the fatherless family it’s just the mother and her children. As I said, this can be the result of the husband’s death, of an unmarried mother, of a separation or divorce. There are also a growing number of motherless families--where the father raises the children, for any of the same reasons. A motherless family may also be fatherless, but still a family with one adult. This is becoming more common in the big cities where a grandmother will raise her daughter’s children while the daughter goes elsewhere to work.One other new kind of family is becoming increasingly more common. A single parent with one or more children will marry again. Perhaps the other parent is also a single parent. Together they will start what is called a blended family, which blends together or combines the children from two other families. How is a blended family formed()
We first think of the traditional or nuclear family. This is a two-generation family, the father and the mother and their own children. Most couples wanted to have four children, two boys, two girls.Some nuclear families, however, may add one or more grandparents to come m live with them, that is three generations. This kind of family with grandparents, parents, and grandchildren is called an extended family. This family type was not very common during the later half of the twentieth century, but it’s becoming more common now as an elderly grandparent moves in to live with a son or daughter. This is more possible now that American homes have become larger. What is interesting, however, is that after the grandchildren move out of the home and start their own families, this extended family shrinks back to a nuclear family, with just two generations again living together, a grandparent and parents, with the grandchildren coming only for occasional visits.Now, the fatherless or motherless family is one kind of what we call a single-parent family. In the fatherless family it’s just the mother and her children. As I said, this can be the result of the husband’s death, of an unmarried mother, of a separation or divorce. There are also a growing number of motherless families--where the father raises the children, for any of the same reasons. A motherless family may also be fatherless, but still a family with one adult. This is becoming more common in the big cities where a grandmother will raise her daughter’s children while the daughter goes elsewhere to work.One other new kind of family is becoming increasingly more common. A single parent with one or more children will marry again. Perhaps the other parent is also a single parent. Together they will start what is called a blended family, which blends together or combines the children from two other families. What is true to the fact in America()
Fire and WaterShundagarh is a village on India’s east-facing coast. It is a village of simple mud and grass houses built on the beach just above the water-line. The Khadra Hills rise immediately behind the village, to a height of one hundred and fifty meters. A simple, good-hearted old man, whose name was Jalpur, farmed two small fields on the very edge of these hills, overlooking Shundagarh. From his fields he could see the fishing-boats that travelled up and down the coast. He could see the children playing on the sand; their mothers washing clothes on the flat stones where the Shiva River flowed into the sea; and their fathers landing the latest catch or repairing nets and telling stories that had no end.All Jalpur owned in the world were the clothes he wore day in and day out, the miserable hut that he slept in at night, a few tools and cooking pots—and his fields. The corn that he grew was all that made life possible. If the weather was kind and the harvest was good, Jalpur could live happily enough—not well, but happily. When the sun was fierce, and there was little or no rain, then he came close to the line between a life which was too hard, and death itself.Last year the weather had been so kind, and the harvest promised to be so good, that Jalpur had been wondering whether he could sell all that he had and live with his son farther up the coast. He had been thinking about doing this for some years. It was his dearest wish to spend his last days with his son and his wife and children. But he would go only if he could give; he would not go if it meant taking food out of the mouths of his grandchildren. He would rather die hungry than do this.On the day on which Jalpur decided that he would harvest his corn, sell it, and move up the coast, he looked out to the sea and saw a huge wave, several kilometres out, advancing on the coast and on the village of Shundagarh. Within ten minutes everyone in Shundagarh would be drowned. Jalpur would have shouted, but the people were too far away to hear. He would have run down the hill, but he was too old to run. He was prepared to do anything to save the people of Shundagarh, so he did the only thing that he could do: he set fire to his corn. In a matter of seconds the flames were rising high and smoke was rising higher. Within a minute the people of Shundagarh were racing up the hill to see what had happened. There, in the middle of his blackened cornfield, they found Jalpur; and there they buried him.On his grave, they wrote the words: Here lies Jalpur, a man who gave, living; a man who died, giving. Shundagarh is a village()
Fire and WaterShundagarh is a village on India’s east-facing coast. It is a village of simple mud and grass houses built on the beach just above the water-line. The Khadra Hills rise immediately behind the village, to a height of one hundred and fifty meters. A simple, good-hearted old man, whose name was Jalpur, farmed two small fields on the very edge of these hills, overlooking Shundagarh. From his fields he could see the fishing-boats that travelled up and down the coast. He could see the children playing on the sand; their mothers washing clothes on the flat stones where the Shiva River flowed into the sea; and their fathers landing the latest catch or repairing nets and telling stories that had no end.All Jalpur owned in the world were the clothes he wore day in and day out, the miserable hut that he slept in at night, a few tools and cooking pots—and his fields. The corn that he grew was all that made life possible. If the weather was kind and the harvest was good, Jalpur could live happily enough—not well, but happily. When the sun was fierce, and there was little or no rain, then he came close to the line between a life which was too hard, and death itself.Last year the weather had been so kind, and the harvest promised to be so good, that Jalpur had been wondering whether he could sell all that he had and live with his son farther up the coast. He had been thinking about doing this for some years. It was his dearest wish to spend his last days with his son and his wife and children. But he would go only if he could give; he would not go if it meant taking food out of the mouths of his grandchildren. He would rather die hungry than do this.On the day on which Jalpur decided that he would harvest his corn, sell it, and move up the coast, he looked out to the sea and saw a huge wave, several kilometres out, advancing on the coast and on the village of Shundagarh. Within ten minutes everyone in Shundagarh would be drowned. Jalpur would have shouted, but the people were too far away to hear. He would have run down the hill, but he was too old to run. He was prepared to do anything to save the people of Shundagarh, so he did the only thing that he could do: he set fire to his corn. In a matter of seconds the flames were rising high and smoke was rising higher. Within a minute the people of Shundagarh were racing up the hill to see what had happened. There, in the middle of his blackened cornfield, they found Jalpur; and there they buried him.On his grave, they wrote the words: Here lies Jalpur, a man who gave, living; a man who died, giving. From his fields Jalpur could see()
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