单选题双向电泳中第二向SDS-聚丙烯酰胺凝胶电泳是根据蛋白质的哪个特点分离的?( ) A．所带电荷 B．等电点 C．分子量 D．分子形状 E．分子大小

单选题框移突变与密码子的哪项特性有关

单选题tRNA中的内含子( )。

单选题下面哪种酶在糖酵解和糖异生中都起作用

单选题小干扰RNA指的是 A.snRNA B.hnRNA C.dsRNA D.siRNA E.miRNA

单选题待测的DNA与标记DNA探针的杂交称为( )。

单选题Several years ago, at the height of the dotcom boom, it was widely assumed that a publishing revolution, in which the printed word would be supplanted by the computer screen, was just around the corner. It wasn't: for many, there is still little to match the joy of reading a printed book and settling down for one hour. But recently some big technology companies, including Google, Amazon, Microsoft and Yahoo, contend that the dream of bringing books online is still very much alive. The digitizing of thousands of volumes of print is not without controversy. On Thursday, Google, the world' s most popular search engine, posted a first installment of books on Google Print. This collaborative effort between Google and several world's leading research libraries aims to make books available to be searched and read online free of charge. Although the books included so far are not covered by copyright, the plan has attracted the rage of publishers. Five large book firms are suing Google for violating copyright on material that it has scanned and, although out of print, is still protected by law. Google has said that it will only publish short extracts from material under copyright unless given express permission to publish more, but publishers are unconvinced. Ironically, many publishers are collaborating with Google Print Publisher, which aims to give readers an online taste of books that are commercially available. The searchable collection of extracts and book information is intended to tempt readers to buy the complete books online or in print form. Amazon, the world's largest online retailer, has made plans to enter the mass e-book market by selling a vast array of goods. Given that Google should impinge upon its central territory, Amazon revealed that it would introduce two new services. Amazon Pages will allow customers to search for key terms in selected books and then buy and read online whatever part they wish. Amazon Upgrade will give customers online access to books they have already purchased as hard copies. Customers are likely to have to pay five cents a page, with the bulk going to the publisher. Microsoft has also joined the online-book trend. In October, the software giant said it would spend around $ 200 million to digitize texts, starting with I50,000 that are in the public domain, to avoid legal problems. It will do so in collaboration with the Open Content Alliance. And on Thursday, coincidentally the same day as Google and Amazon announced their initiatives, Microsoft released details of a deal with the British Library, the country's main reference library, to digitize some 25 million pages ; these will be made available through MSN Book Search, which will be launched next year.

单选题下列何种物质与苹果酸穿梭过程无关

单选题关于细胞癌基因描述不正确的是 A.存在于DNA和RNA肿瘤病毒 B.也称为原癌基因 C.激活后导致肿瘤 D.正常细胞基因组中存在 E.维持正常细胞生长等功能

单选题在切口平移标记DNA探针时只能使用( )。

单选题基因诊断的常用技术方法不包括( ) A．RFLP分析 B．基因测序 C．基因剔除 D．核酸分子杂交 E．PCR/SSCP

单选题复制子是______。 A．细胞分离期间复制产物被分离之后的DNA片段 B．复制的DNA片段和在此过程中所需的酶和蛋白 C．任何自发复制的DNA序列(它与复制起始点相连) D．复制起点和复制叉之间的DNA片段

单选题磺胺类药物能竞争抑制二氢叶酸还原酶是因为其结构相似于( )(2004年)

单选题A．胞质B．线粒体和胞质C．微粒体D．细胞核E．溶酶体

单选题原核生物和真核生物翻译起始的不同点是 A.真核生物先靠Shine-Dalgarno序列使mRNA结合核糖体 B.真核生物帽结合蛋白是翻译起始因子之一 C.IF比eIF种类多 D.原核生物和真核生物使用不同起始密码 E.原核生物有TATAAT作为翻译起始序列，真核生物则是TATA

单选题RNA聚合酶Ⅰ的功能是( )。

单选题DNA受热变性时，出现的现象是( )(2005年)

单选题6-巯基嘌呤治疗肿瘤的机制是

单选题结合到小亚基时需要的物质是A.IF-2及ATPB.IF-2及GTPC.IF-2及CTPD.IF-2及UTPE.IF-3及TTP

单选题有关操纵子学说的正确论述是( ) A．操纵子调控系统是真核生物基因调控的主要方式 B．操纵子调控系统是原核生物基因调控的主要方式 C．操纵子调控系统由结构基因、启动子和操纵基因组成 D．诱导物与操纵基因结合启动转录 E．诱导物与启动子结合而启动转录