单选题A．DNA复制或转录时模板链的方向B．DNA复制时前导链的方向C．DNA复制叉的前进方向D．DNA复制时冈崎片段的方向E．DNA或RNA合成时核酸链的延伸方向

单选题脂类在肠道消化后吸收不涉及的中间产物是

单选题免疫球蛋白基因的增强子只有在B淋巴细胞内活性才最高，表明增强子具有______特性。

单选题下列哪个是人体非必需氨基酸

单选题有关逆转录的论述，哪一项是错误的?( )

单选题下列哪项能特异激活蛋白激酶C

单选题17-酮类固醇主要来源于

单选题氨基酸与蛋白质的共性是( )。

单选题下列不属于DNA聚合酶的是______ A．端粒酶 B．Klenow片段 C．Taq DNA聚合酶 D．反转录酶E．DNA连接酶

单选题下列关于白蛋白的叙述错误的是 A.是单纯蛋白质，不含任何糖基 B.在生理pH条件下带负电荷 C.分子量小，故在维持血浆胶体渗透压中不起主要作用 D.在碱性介质中电泳时比所有球蛋白泳动快 E.半饱和硫酸铵可使之从血浆中沉淀出来

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

单选题根据F.Crick中心法则，遗传信息的传递方式是

单选题下列______是氨基酸和蛋白质所共有的性质。

单选题自然界最常见的单核苷酸是（　　）。【2003年考试真题】

单选题Low levels of literacy and numeracy have a damaging impact on almost every aspect of adults, according to a survey published yesterday, which offers (1) of a developing underclass. Tests and (2) with hundreds of people born in a week in 1958 graphically illustrated the (3) of educational underachievement. The effects can be seen in unemployment, family (4) , low incomes, depression and social inactivity. Those who left school at 16 with poor basic skills had been employed for up to four years less than good readers (5) they reached 37. Professor John Bynner, of City University, who carried the research, said that today’s (6) teenagers would even encounter greater problems because the supply of (7) jobs had shrunk. Almost one fifth of the 1,700 people interviewed for yesterday’s report had poor literacy and almost half (8) with innumeracy, a proportion (9) other surveys for the Basic Skills Agency. Some could not read a child’s book, and most found difficult (10) written instruction. Poor readers were twice as likely to be a low wage and four times likely to live in a household where partners worked. Women in this (11) were five times as likely to be (12) depressed, (13) both tended to feel they had no control over their lives, and to trust others (14) . Those who had low literacy and numeracy were seldom (15) in any community organization and less likely than others to (16) in a general election. There had been no (17) in the literary level of (18) reporting problems. Alan Wells, the agency’s director, said: “ The results emphasize the dangers of developing an underclass people, who were out of work, (19) depressed and often labeled themselves as (20) . There is a circle of marginalization, with the dice against these people and their families.”

单选题血清转铁蛋白增高的是

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