单选题关于PCR的基本成分叙述错误的是 A.特异性引物 B.耐热性DNA聚合酶 C.dNTP D.含有Zn2+的缓冲液 E.模板

单选题下列哪一种化合物是胆固醇合成原料

单选题A．甲硫基B．羟基C．巯基D．亚氨基E．咪唑基

单选题基因工程技术中实现目的基因与载体DNA连接的酶是( )。

单选题严重肝病时，机体各器官会发生出血倾向，主要原因是 A.维生素A减少 B.维生素B6减少 C.维生素C减少 D.维生素E减少 E.维生素K减少

单选题Prince Klemens Von Metternich, foreign minister of the Austrian Empire during the Napoleonic era and its aftermath, would have no trouble recognizing Google. To him, the world's most popular web-search engine would closely resemble the Napoleonic France that in his youth humiliated Austria and Europe's other powers. Its rivals—Yahoo!, the largest of the traditional web gateways, eBay, the biggest online auction and trading site, and Microsoft, a software empire that owns MSN, a struggling web portal—would look a lot like Russia, Prussia, and Austria. Metternich responded by forging an alliance among those three monarchies to create a "balance of power" against France. Google's enemies, he might say, ought now to do the same thing. Google announced two new conquests on August 7th. It struck a deal with Viacom, an "old" media firm, under which it will syndicate video clips from Viacom brands such as MTV and Nickelodeon to other websites, and integrate advertisements into them. This makes Google the clear leader in the fledgling but promising market for web-video advertising. It also announced a deal with News Corporation, another media giant, under which it will pro-vide all the search and text-advertising technology on News Corporation's websites, including My Space, an enormously popular social-networking site. These are hard blows for Yahoo! and MSN, which had also been negotiating with News Corporation. Both firms have been losing market share in web search to Google over the past year—Google now has half the market. They have also fallen further behind in their advertising technologies and networks, so that both make less money than Google does from the same number of searches. Safa Rashtchy, an analyst at Piper Jaffray, a securities firm, estimates that for every advertising dollar that Google makes on a search query, Yahoo! makes only 60-70cents. Last month Yahoo! said that a new advertising algorithm that it had designed to close the gap in profitability will be delayed, and its share price fell by 22% , its biggest-ever one-day drop. MSN is further behind Google than Yahoo! in search, and its parent, Microsoft, faces an even more fundamental threat from the expansionist new power. Many of Google's new ventures beyond web search enable users to do things free of charge through their web browsers that they now do using Microsoft software on their personal computers. Google offers a rudimentary but free online word processor and spreadsheet, for instance. The smaller eBay, on the other hand, might in one sense claim Google as an ally. Google's search results send a lot of traffic to eBay's auction site, and eBay is one of the biggest advertisers on Google's network. But the relationship is imbalanced. An influential re-cent study from Berkeley's Haas School of Business estimated that about 12% of eBay's revenues come indirectly from Google, whereas Google gets only 3% of its revenues from eBay. Worst of all for eBay, Google is starting to undercut its core business. Sellers are setting up their own websites and buying text advertisements from Google, and buyers are using its search rather than eBay to connect with sellers directly. As a result, "eBay would be wise to strike a deep partnership with Yahoo! or Microsoft in order to regain a balance of power in the industry," said the study's authors, Julien Decot and Steve Lee, sounding like diplomats at the Congress of Vienna in 1814.

单选题信号肽的特点不包括：

单选题蛋白质三级结构的形成和稳定主要靠的键或作用力不包括

单选题下列哪项不属于真核生物基因的顺式作用元件______ A.激素反应元件 B.衰减子 C.启动子 D.沉默子 E.增强子

单选题体内生成核糖的主要途径是(　　　)

单选题2003年诺贝尔化学奖授予研究生物膜上通道蛋白的科学家，他们阐明了______。

单选题RNAi技术的基本程序主要为 A.siRNA对目标RNA的干扰、确定干扰靶点、合成siRNA B.确定干扰靶点、合成siRNA、siRNA对目标RNA的干扰 C.siRNA对目标RNA的干扰、合成siRNA、确定干扰靶点 D.确定干扰靶点、siRNA对目标RNA的干扰、合成siRNA E.合成siRNA、确定干扰靶点、siRNA对目标RNA的干扰

单选题下列事件中，哪些发生在RNA合成过程中?( )

单选题雄激素对物质代谢最显著的一项重要作用是______。

单选题原核生物和真核生物中的rRNA具有的相同结构是 A.18SRNA B.5SrRNA C.5.8SrRNA D.28SrRNA E.16SrRNA

单选题胃蛋白酶的最适pH是

单选题针对配基的生物学特异性的蛋白质分离方法是______。

单选题理想冠桩外形的要求是

单选题血氨升高的主要原因是（　　）。

单选题建cDNA文库时，首先需分离细胞的( )。