单选题下列哪种辅酶中不含维生素

单选题以下各种物质是自由基的是______ A.CH3 B.OH- C.H+ D.O2 E.H2O

单选题下列哪种物质不是嘌呤核苷酸从头合成的直接原料

单选题下列叙述哪一种是正确的?______

单选题与琥珀酰辅酶A生成有关的化合物为(　　　)

单选题氨基酸在肝、肾中将氨基转移给

单选题DNA变性时断裂的键为(　　　)

单选题磷脂分子最重要的特征是

单选题利福平是RNA合成起始的抑制剂，这是由于利福平能够与E.coil的RNA聚合酶中的______亚基结合。

单选题原核生物的核糖体大亚基是______ A．30S B．40S C．50S D．60SE．70S

单选题限制性片段长度多态性是( )。

单选题基因表达指的是 A.复制的过程 B.转录的过程 C.逆转录的过程 D.翻译的过程 E.转录及翻译的过程

单选题合成尿素的主要器官是

单选题链长为10000bp的闭合环状DNA处于完全松弛状态时，其缠绕数大约为：______。 A.10000 B.950 C.100 D.9.5

单选题Should anyone much care whether an American boy living overseas gets six vicious thwacks on his backside? So much has been argued, rejoined and rehashed about the case of Michael Fay, an 18-year-old convicted of vandalism and sentenced to a caning in Singapore, that an otherwise sorry little episode has shaded into a certified International Incident, complete with intercessions by the U. S. head of state. An affair has outraged American libertarians even as it has animated a general debate about morality East and West and the proper functioning of U.S. law and order. Which, to all appearances, is what Singapore wanted. The question of whether anyone should care about Michael Fay is idle. though Singapore officials profess shock at the attention his case had drawn, they know Americans care deeply about the many sides of this issue. Does a teenager convicted of spraying cars with easily removable paint deserve half a dozen powerful strokes? At what point does swift, sure punishment become torture? By what moral authority can America, with its high rates of lawlessness and license, preach of a safe society about human rights? The caning sentence has concentrated minds wondrously on an already lively domestic debate over what constitutes a due balance between individual and majority rights. Too bad Michael Fay has become a focus for this discussion. Not only does he seem destined to be pummeled and immobilized, but the use of Singapore as a standard for judging any other society, let alone the cacophonous U. S. , is fairly worthless. To begin with, Singapore is an offshore republic that tightly limits immigration. Imagine crime-ridden Los Angeles, to which Singapore is sometimes contrasted, with hardly any inflow of the hard-luck, often desperate fortune seekers who flock to big cities. Even without its government's disciplinary measures, Singapore more than plausibly would be much the same as it is now. An academic commonplace today is that the major factor determining social peace and prosperity is culture--a sense of common identity, tradition and values. Unlike Singapore, though, the U. S. today is a nation in search of a common culture, trying to be a universal society that assimilates the traditions of people from all over the world. Efforts to safeguard minority as well as individual rights have produced a gridlock in the justice system. Its troubles stem more from the decay of family life than from any government failures. Few societies can afford to look on complacently. As travel eases and cultures intermix, the American experience is becoming the world's. The circumstances of this affair--evidently no Singaporean has ever been punished under the Vandalism Act for defacing private property--suggest that Singapore has used Fay as an unwilling point man in a growing quarrel between East and West about human rights.

单选题第Ⅱ类内含子的剪接与前体mRNA剪接的相似之处是( )。

单选题转座过程中伴随有靶点序列的倍生，这是因为：

单选题成熟红细胞获得能量的唯一途径是

单选题关于2，3-BPG的叙述错误的是 A.2，3-BPG是红细胞内能量的贮存形式 B.2，3-BPG与去氧血红蛋白的亲和力高 C.2，3-BPG降低血红蛋白对氧的亲和力 D.2，3-BPG调节血红蛋白的运氧功能 E.2，3-BPG与氧合血红蛋白的亲和力高

单选题大部分限制性内切酶识别的序列呈