单选题DNA双链断裂的感应因子是( ) A．ATR B．ATM C．Chk1 D．Chk2 E．Cdc25A

单选题下列哪个可以抑制复合体Ⅳ

单选题E.coil的RNA聚合酶σ因子有不同的形式，其中______参与绝大多数基因的转录。

单选题结构基因的编码产物不包括______ A.snRNA B.hnRNA C.启动子 D.转录因子 E.核酶

单选题下列RNA序列能形成分子内茎-环结构的是：

单选题与mRNA的GCU密码子对应的tRNA的反密码子是( )。

单选题下列叙述哪个是正确的______。 A．C值与生物体的形态学复杂性成正相关 B．C值与生物体的形态学复杂性成负相关 C．每个门的最小C值与生物体的形态学复杂性是大致相关的

单选题哺乳动物核糖体大亚基的沉降常数是______ A.30S B.40S C.50S D.60S E.70S

单选题原核生物所有编码合成代谢酶的基因在转录起始位点的上游10和35碱基处都有保守序列。对此最好的解释是，这里是( )的结合位点。

单选题A．碱性肥皂水灌肠B．中性透析液结肠透析C．弱酸性透析液结肠透析D．酸性利尿剂E．碱性利尿剂

单选题A．F0F1复合体B．F0C．F1的β亚基D．F1的γ亚基E．F1的ε亚基

单选题Americans usually consider themselves a friendly people. Their friendships, however, tend to be shorter and more casual than friendships among people from other cultures. It is not uncommon for Americans to have only one close friend during their life-time, and consider other "friends" to be just social acquaintances. This attitude probably has something to do with American mobility and the fact that Americans do not like to be dependent on other people. They tend to "compartmentalize" friendships, having "friends at work" ,"friends on the softball team", "family friends", etc. Because the United States is a highly active society, full of movement and change, people always seem to be on the go. In this highly charged atmosphere, Americans can sometimes seem brusque or impatient. They want to get to know you as quickly as possible and then move on to something else. Sometimes, early on, they will ask you questions that you may feel are very personal. No insult is intended; the questions usually grow out of their genuine interest or curiosity, and their impatience to get to the heart of the matter. And the same goes for you. If you do not understand certain American behavior or you want to know more about them, do not hesitate to ask them questions about themselves. Americans are usually eager to explain all about their country or anything "American" in which you may be interested. So much so in fact that you may become tired of listening. It doesn't matter, because Americans tend to be uncomfortable with silence during a conversation. They would rather talk about the weather or the latest sports scores, for example, than deal with silence. On the other hand, don't expect Americans to be knowledgeable about international geography or world affairs, unless those subjects directly involve the United States. Because the United States is not surrounded by many other nations, some Americans tend to ignore the rest of the world.

单选题组成有机体的所有不同细胞都共享( ) A．不同基因组 B．一个基因组 C．二个基因组 D．三个基因组 E．多个基因组

单选题嘌呤霉素作为蛋白合成抑制剂，是因为它( )。

单选题可促进胶原蛋白合成的维牛素是

单选题在哺乳动物细胞中，RNA编辑( )。

单选题下列哪种储存方式可以长时间保存蛋白质( ) A．溶液状态常温保存 B．溶液状态4℃保存 C．硫酸铵溶液中以沉淀方式4℃保存 D．硫酸铵沉淀蛋白，离心后在液氮中保存 E．冻干的粉末形式保存

单选题DNA复制时，不参与的酶是 A.DNA指导的DNA聚合酶 B.DNA连接酶 C.拓扑异构酶 D.解链酶 E.限制性内切酶

单选题下列关于核内复制的说法不正确的是( )。

单选题动脉血PaO 2 的参考值是