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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. Where are most likely to be affected by caner-inducing agents according to the passage()
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只要社会主义物质文明建设搞好了，社会主义精神文明建设就自然搞好了。
简述历史观的基本问题和唯物史观创立的伟大意义。
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. Who usually looks after the children in a both motherless and fatherless family in America()
在新民主主义革命时期，只有当民族资产阶级拥护革命时，才要保护民族资本主义。
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