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1、2022年考博英语-中南大学考前拔高综合测试题（含答案带详解）1. 单选题Until about five years ago, the very idea that peptide hormones might be made anywhere in the brain besides the hypothalamus was astounding- Peptide hormones, scientists thought, were made by endocrine glands and the hypothalamus was thought to be the brains only
2、 endocrine gland. What is more, because peptide hormones cannot cross the blood-brain barrier; researchers believed that they never got to any part of the brain other than the hypothalamus, where they were simply produced and then released into the bloodstream.But these beliefs about peptide hormone
3、s were questioned as laboratory after laboratory found that antiserums to peptide hormones, when injected into the brain, bind in places other than the hypothalamus, indicating that either the hormones or substances that cross-react with the antiserums are present. The immunological method of detect
4、ing peptide hormones by means of antiserums, however, is imprecise. Cross-reactions are possible, and this method cannot determine whether the substances detected by the antiserums really are the hormones, or merely close relatives. Furthermore this method cannot be used to determine the location in
5、 the body where the detected substances are actually produced.New techniques of molecular biology, however, provide a way to answer these questions. It is possible to make specific complementary DNAs (CDNAs) that can serve as molecular probes to seek out the messenger RNAs (mRNAs) of the peptide hor
6、mones. If brain cells are making the hormones, the cells will contain these mRNAs. If the products the brain cells make resemble the hormones but are not identical to them, then the cDNAs should still bind to these mRNAs, but should not bind as tightly as they would to mRNAs for the true hormones. T
7、he cells containing these mRNAs can then be isolated and their mRNAs decoded to determine just what their protein products are and how closely the products resemble the true peptide hormones.The molecular approach to detecting peptide hormones using cDNA probes should also be much faster than the im
8、munological method because it can take years of tedious purifications to isolate peptide hormones and then develop antiserums to them. Roberts, expressing the sentiment of many researchers, states: “I was trained as an endocrinologist. But it became clear to me that the field of endocrinology needed
9、 molecular biology input. The process of grinding out protein purifications is just too slow.”If, as the initial tests with cDNA probes suggest, peptide hormones really are made in the brain in areas other than the hypothalamus, a theory must be developed that explains their function in the brain. S
10、ome have suggested that the hormones are all growth regulators, but Rosens work on rat brains indicates that this cannot be true. A number of other researchers propose that they might be used for intercellular communication in the brain.1.Which of the following titles best summarizes the passage?2.T
11、he passage suggests that a substance detected in brain by use of antiserums to peptide hormones may（ ）.3.The passage implies that, in doing research on rat brains, Rosen discovered that（ ）.4.Which of the following is a way in which the immunological method of detecting peptide hormones differs from
12、the molecular method?问题1选项A.Is Molecular Biology the Key to Understanding Intercellular Communication in the Brain?B.Molecular Biology: Can Researchers Exploit Its Techniques to Synthesize Peptide Hormones?C.The Advantages and Disadvantages of the Immunological Approach to Detecting Peptide Hormones
13、.D.Peptide Hormones: How Scientists Are Attempting to Solve Problems of Their Detection.问题2选项A.have been stored in the brain for a long period of time and to Understand Their FunctionB.play no role in the functioning of the brainC.have been produced in some part of the body other than the brainD.pla
14、y an important role in the functioning of hypothalamus问题3选项A.peptide hormones are used for intercellular communicationB.complementary DNAs do not bind to cells producing peptide hormonesC.products closely resembling peptide hormones are not identical to peptide hormoneD.some peptide hormones do not
15、function as growth regulators问题4选项A.The immunological method uses substances that react with products of hormone-producing cells, whereas the molecular method uses substances that react with a specific component of the cells themselves.B.The immunological method has produced results consistent with
16、long-held beliefs about peptide hormones, whereas the molecular method has produced results that upset these beliefs.C.The immunological method uses probes that can only bind with peptide hormones, whereas the molecular method uses probes that bind with peptide hormones and substances similar to themD.The immunological method can only be used to test for the pre
