单选题可以作为嘌呤合成的原料是

单选题下列物质分解时，不能生成胆红素的是 A.脂蛋白 B.血红蛋白 C.肌红蛋白 D.细胞色素c E.过氧化氢酶

单选题氨基酸序列构成了蛋白质的______。

单选题原核和真核生物的基因都具有______ A.操纵元件 B.顺式作用元件 C.反式作用因子 D.内含子 E.RNA聚合酶结合位点

单选题乳糖操纵子的体内生理诱导剂是( ) A．β-半乳糖苷酶 B．透酶 C．葡萄糖 D．乳糖 E．别乳糖

单选题大肠杆菌中参与转录终止调控的是：

单选题正常人血浆清蛋白与球蛋白比值为

单选题原核生物RNA聚合酶识别的启动子位于( )。

单选题下列具有基因内启动子是______。 A．U6 snRNA基因 B．tRNA基因 C．mRNA基因 D．18S-5.8S-28S基因

单选题关于ATP合酶叙述正确的是 A.它是呼吸链复合体Ⅳ的一个亚基 B.F1和F0都是亲水的 C.F0催化ATP的生成与释放 D.ATP合酶参与Na+，K+-ATP酶的组成 E.F0是H+的通道

单选题RT-PCR中不涉及的物质是 A.探针 B.cDNA C.逆转录酶 D.RNA E.dNTP

单选题细胞核运输的方向性受Ran蛋白状态直接控制，______存在于细胞核内。

单选题在天然蛋向质的组成中，不含有的氨基酸是( )(2009年)

单选题原核核糖体上结合氨基酰tRNA的氨基酰位的位置是

单选题A．氯霉素B．GTP酶C．转肽酶D．蛋白激酶E．链霉素

单选题It is generally recognized in the world that the second Gulf War in Iraq is a crucial test of high-speed web. For decades, Americans have anxiously (1) each war through a new communication (2) , from the early silent film of World War I to the 24-hour cable news (3) of the first Persian Gulf War. Now, (4) bombs exploding in Baghdad, a sudden increase in wartime (5) for online news has become a central test of the (6) of high-speed Internet connections. It is also a good (7) both to attract users to online media (8) and to persuade them to pay for the material they find there, (9) the value of the Cable News Network persuaded millions to (10) to cable during the last war in Iraq. (11) by a steady rise over the last 18 months in the number of people with high-speed Internet (12) , now at more than 70 million in the United States, the web sites of many of the major news organizations have (13) assembled a novel collage (拼贴) of (14) video, audio reports, photography collections, animated weaponry (15) , interactive maps and other new digital reportage. These Internet services are (16) on the remarkable abundance of sounds and images (17) from video cameras (18) on Baghdad and journalists traveling with troops. And they have found a (19) audience of American office workers (20) their computers during the early combat.

单选题仅仅使DNA单链或者双链断裂而对RNA不起作用的药物是( ) A．博来霉素 B．嘌呤霉素 C．新霉素 D．放线菌素 E．新霉素

单选题膜结构功能的特殊性主要取决于______。

单选题下列DNA中哪一种是单拷贝DNA?( )

单选题当点突变没有带来限制性酶切位点的改变时，不可以采用的诊断技术是( ) A．测序 B．RFLP C．PCR-ASO D．AS-PCR E．核酸分子杂交