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  3. Three years ago, researchers announced the discovery of human genes that wer

Three years ago, researchers announced the discovery of human genes that wer

游客2025-03-24  49
问题     Three years ago, researchers announced the discovery of human genes that were capable of turning ordinary cells into malignant ones. The news met with some skepticism. Experts asked how a single gene could cause such a dramatic change. Why does cancer take years or even decades to develop if it is caused by such a simple and direct process? In last week’s issue of the, three research teams answered those questions by setting forth a new model for understanding the role of oncogenes in cancer.
    Each group found that it does in fact take more than a single gene to produce cancer in normal cells. Teams at M. I. T and Cold Spring Harbor Laboratory on Long Island, N. Y. , reported that they could induce cancer in normal rat cells only by inserting at least two types of oncogene into the cells. "A single oncogene produced some changes, but not cancer," explained molecular biologist Robert Weinberg of MIT. It took two genes acting cooperatively to produce a tumor. In other cases, it might take three or more.
    A British team confirmed the multistep cancer scenario by showing that a particular oncogene caused a tumor in hamster cells only if they had first been exposed to a carcinogenic chemical. The chemical alone and the oncogene alone did not cause cancer, both were necessary. While the discovery has no immediate implication for treatment of cancer, it helps explain why the disease develops slowly and why its incidence rises with age. "Even if one part of the process occurs," says Weinberg, "you might not have the second step for another 20 years. " [br] Other scientists were skeptical of the report because ______.
选项 A、cancer takes a long time to develop
B、single genes were not thought to cause cancer
C、genes would take years or even decades to bring about cancer
D、the researcher’s report was too simple
答案 A
解析 本题是细节题。该题内容出现在文中第一段的中间部分。因为报告认为癌症是由单一基因造成的，故另一些科学家对如此简单的直接的过程需要几年甚至十几年的发展而感到怀疑，所以A选项是正确答案。B选项与文中内容不符，这不是科学家产生怀疑的根本原因，C选项不合题意，文中科学家已经宣称单个基因也可能引发癌症。D选项内容文中没有涉及。
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