单选题 bicoid蛋白是一类转录因子，它促进胚胎( )发育的差异。 A、背腹轴 B、前后轴 C、前部 D、腹部

单选题自然界最常见的单核苷酸是（　　）。【2003年考试真题】

单选题释放因子的主要功能是 A.诱导肽酰转移酶显示酯酶活性 B.诱导转位酶活化显示酯酶活性 C.使肽酰-tRNA从核糖体中释放 D.阻止氨基酰-tRNA进入核糖体 E.具有GTP酶活性，使GTP水解

单选题A．丙二酰CoAB．脂肪酰CoAC．羟丁酸D．乙酰乙酰CoA

单选题血清转铁蛋白增高的是

单选题以下哪种DNA结构是起始DNA同源重组所必需的?( ) A．末端平齐的双链DNA断裂 B．5'末端自由的一段DNA单链区域 C．3'末端自由的一段DNA单链区域 D．以上任何一种都可以

单选题RNA聚合酶催化转录时，其底物为

单选题有关逆转录的论述，哪一项是错误的?( )

单选题着色性干皮病是人类的一种遗传性皮肤病，患者皮肤经阳光照射后易发展为皮肤癌，该病的分子机制是( ) A．细胞膜通透性缺陷引起迅速失水 B．在阳光下使温度敏感转移酶类失活 C．因紫外线照射诱导了有毒力的前病毒 D．细胞不能合成类胡萝卜素型化合物 E．DNA修复系统有缺陷

单选题下列哪项能特异激活蛋白激酶C

单选题结合RNA聚合酶并启动转录的DNA序列是 A.启动子 B.增强子 C.沉默子 D.操纵子 E.衰减子

单选题下列关于PCR引物设计的说法错误的是 A.每条引物自身不应有稳定的发卡结构 B.上下游引物之间不宜形成稳定的二聚体结构 C.引物的5'-末端必须和模板严格配对结合 D.引物的3'-末端必须和模板严格配对结合 E.引物与非特异扩增区的序列无同源性

单选题The question of whether war is inevitable is one which has concerned many of the world's great writers. Before considering this question, it will be useful to introduce some related concepts. Conflict, defined as opposition among social entities directed against one another, is distinguished from competition, defined as opposition among social entities independently striving for something which is in inadequate supply. Competitors may not be aware of one another, while the parties to a conflict are. Conflict and competition are both categories of opposition, which has been defined as a process by which social entities function in the disservice of one another. Opposition is thus contrasted with cooperation, the process by which social entities function in the service of one another. These definitions are necessary because it is important to emphasize that competition between individuals or groups is inevitable in a world of limited resources, but conflict is not. Conflict, nevertheless, is very likely to occur, and is probably an essential and desirable element of human societies. Many authors have argued for the inevitability of war from the premise that in the struggle for existence among animal species, only the fittest survive. In general, however, this struggle in nature is competition, not conflict. Social animals, such as monkeys and cattle, fight to win or maintain leadership of the group. The struggle for existence occurs not in such fights, but in the competition for limited feeding areas and for occupancy of areas free from meat-eating animals. Those who fail in this competition starve to death or become victims to other species. This struggle for existence does not resemble human war, but rather the competition of individuals for jobs, markets, and materials. The essence of the struggle is the competition for the necessities of life that are insufficient to satisfy all. Among nations there is competition in developing resources, trades, skills, and a satisfactory way of life. The successful nations grow and prosper; the unsuccessful decline. While it is true that this competition may induce efforts to expand territory at the expense of others, and thus lead to conflict, it cannot be said that war-like conflict among nations is inevitable, although competition is.

单选题在已知序列的情况下获得目的DNA最常用的是

单选题A．酸性蛋白质 B．支链氨基酸C．芳香族氨基酸 D．亚氨基酸E．含硫氨基酸

单选题通过鸟氨酸循环生成尿素时，其分子中的两个氮原子一个直接来自游离的氨，另一个直接来源于

单选题蛋白质在等电点时是

单选题干扰素指的是 A.病毒本身存在的物质 B.细菌产生的物质 C.根据竞争性抑制原理设计的物质 D.病毒感染后诱导细胞合成的物质 E.抗生素中的一种

单选题决定糖酵解途径最主要的是(　　　)

单选题已知基因A和B都是X连锁的，下列何种杂交所得的子代能确定位点间的重组率(假定雄性是异配性别，而且两性别均可发生交换)。______ A.雌AB/ab×AB/Y雄 B.雌Ab/aB×ab/Y雄 C.雌ab/AB×Ab/Y雄 D.上述各种杂交都不对