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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The quantum theory states （ ）, as light, is given off and absorbed in definite units called quanta or photons.问题1选项A.energy thatB.that it is energyC.it is energyD.that energy【答案】D【解析】考查宾语从句。states是谓语，后面接一个句子做宾语。宾语从句需要一个引导词that, 另外 宾语从句还缺少主语，故D项正确。句意：量子理论认为，能量，比如光
2、，是以量子或光子的基本单位来释放和吸收的。2. 单选题The chemical formula of deoxyribonucleic acid (DNA) is now well established. The molecule is a very long chain, the backbone of which consists of a regular alternation of sugar and phosphate groups. To each sugar is attached a nitrogenous base, which can be of four differe
3、nt types. Two of the possible basesadenine and guanine are purines, and the other two thymine and cytosine are pyrimidines. So are as is known, the sequence of bases along the chain is irregular. The monomer unit, consisting of phosphate, sugar and base, is known as a nucleotide.The first feature of
4、 our structure which is of biological interest is that it consists not of one chain, but of two. These two chains are both coiled around a common fiber axis. It has often been assumed that since there was only one chain in the chemical formula there would only be one in the structural unit. However,
5、 the density, taken with the X-ray evidence, suggests very strongly that there are two.The other biologically important feature is the manner in which the two chains are held together. This is done by hydrogen bonds between the bases. The bases are joined together in pairs, a single base from one ch
6、ain being hydrogen-bonded to a single base from the other. The important point is that only certain pairs of bases will fit into the structure. One member of a pair must be a purine and the other a pyrimidine in order to bridge between the two chains. If a pair consisted of two purines, for example,
7、 there could not be room for it.We believe that the bases will be present almost entirely in their most probable forms. If this is true, the conditions for forming hydrogen bonds are more restrictive, and the only pairs of bases possible are: adenine with thymine, and guanine with cytosine. Adenine,
8、 for example, can occur on either chain; but when it does, its partner on the other chain must always be thymine.The phosphate-sugar backbone of our model is completely regular, but any sequence of the pairs of bases can fit into the structure. It follows that in a long molecule many different permu
9、tations are possible, and it therefore seems likely that the precise sequence of bases is the code which carries the genetical information. If the actual order of the bases on one of the pair of chains were given, one could write down the exact order of the bases on the other one, because of the spe
10、cific pairing. Thus, one chain is, as if were, the complement of the other, and it is this feature which suggests how the deoxyribonucleic acid molecule might duplicate itself.1.The authors use the word “backbone” (underlined in 1th and 5th paragraphs) to indicate that （ ）.2.In the second paragraph,
11、 what do the authors claim to be a feature of biological interest?3.Based on the passage, the authors statement “If a pair consisted of two purines, for example, there would not be room for it” (italicized) implies that pair（ ）.4.The authors9 use of the words “exact,” “specific,” and “complement” bl
12、ackened in the final paragraph functions mainly to（ ）.问题1选项A.only very long chains of DNA can be taken from an organism with a spinal columnB.the main structure of a chain in a DNA molecule is composed of repeating unitsC.a chain in a DNA molecule consists entirely of phosphate groups or of sugars.D
13、.nitrogenous bases form the main structural unit of DNA问题2选项A.DNA consisting of two chains.B.The common fiber axis.C.The X-ray evidence.D.The chemical formula of DNA问题3选项A.of purines would be larger than the space between a sugar and a phosphate groupB.of purines would be larger than a pair consisti
14、ng of a purine and a pyrimidineC.of pyrimidines would be larger than a pair of purinesD.consisting of a purine and a pyrimidine would be larger than a pair of pyrimidine问题4选项A.confirm that the nucleotide sequences are known for most molecules of DNAB.counter the claim that the sequences of bases alo
15、ng a chain can occur in any orderC.support the claim that the phosphate-sugar backbone of the authors model is completely regularD.emphasize how one chain of DNA may serve as template to be copied during DNA replication【答案】第1题:B第2题:A第3题:B第4题:D【解析】1.判断推理题。由第一段中 The molecule is a very long chain, the
16、backbone of which consists of a regular alternation of sugar and phosphate groups. DNA 分子是一个非常长的链条，其支柱由糖和磷酸基有规律的交替组合构成。与第五段中The phosphate-sugar backbone of our model is completely regular, but any sequence of the pairs of bases can fit into the structure. 我们人类的DNA分子模式的磷酸糖支柱完全是有规律的，不过成对的含氮碱基的任何排序都可以纳入该结构。可知
