单选题吖啶类诱导的突变体，回复突变时最好用。( )

单选题呼吸链中的递氢体是(　　　)

单选题______具有侵染性。

单选题需要维生素B 6 作为辅酶的氨基酸反应有______。

单选题下列除了哪项外均属类固醇激素

单选题A few milliamps of electricity can cause plants to increase synthesis of chemicals. These compounds often also have a pharmacological (related to medicine) or commercial value, so the trick could be used to help increase yields of commercially useful biologicals. Artemisinic acid, from sweet wormwood, for example, is used in malarial medications, and shikonin (紫草素), from the purple gromwell plant, is used against skin infections. Researchers have long known that stressing plants can force them to take defensive action, often ramping up the production of protective chemicals that, for example, make them more resistant to insect attack. It has become common practice to stress such plants into increasing their yields. This is usually clone using physical stress elicitors (诱导子), including bits of the micro-organisms that normally attack the plants, or irritants made from metallic compounds such as copper chloride. These are effective, but they come at a cost. Most elicitors are toxic to plants and can build up in tissues, making it necessary to occasionally "clean" a plant of the chemicals so they keep having the same effect. Recently, research groups at the University of Arizona in Tucson found that the application of an electric current to the hairy roots of the poisonous herb Hyoscyamus muticus stimulated the production of the herb's toxin hyoscyamine (天仙子胺). This unpublished finding inspired Hans Van Etten, also of the University of Arizona, and his colleagues to test sub-lethal levels of electrical currents on other plants, to assess electricity's potential to elevate chemical production. The researchers exposed eight different plant species (ranging from Japanese pagoda tree seedlings to pea plants) to weak electrical currents of 30 milliamps. Seven of the plants increased their production o defensive chemicals. The average boost of chemical production was 20 times, they report in Biotechnology Progress. One plant, a type of alfalfa, increased its chemical yield by 168 times. These values are very similar to those achieved using chemical elicitors, and seem to have no lethal effects-just a negative effect on growth. The treatment can be used over and over again without the build-up of any unwanted material. The useful compounds would be very easy to harvest: they simply pour out into solution if the plants are grown hydroponically. "The fact that we can use electricity instead of toxic materials to elicit chemical production is very exciting because it means we get to look at how these chemicals form without having to constantly add and remove toxins from the system," says Van Etten. "This is a really novel and creative approach that I've never seen before," says plant metabolic engineer Fabricio Medina Bolivar from Arkansas State University in Jonesboro. "The possibilities for using electricity with plants in this way are absolutely tremendous. /

单选题某种人类肿瘤细胞染色体数目为92条，称为( )。

单选题关于脂肪合成所需原料的叙述，错误的是

单选题真核生物染色体复制过程中，亲代组蛋白八聚体和新合成组蛋白八聚体的装配方式是： A．全保留 B．半保留 C．随机 D．半随机

单选题DNA测序发现目的基因(5"-exon1-intronl-exon2-intron2-exon3-3")的intron2的5"端GU发生突变，导致拼接体无法识别，可推测该突变基因的成熟mRNA的序列为：

单选题氨基酸脱氨基可生成相应的α-酮酸，后者在体内参与合成

单选题以下关于原核生物RNA聚合酶的核心酶的叙述，哪一项是正确的?( ) A．核心酶可以与DNA结合，但不能催化以DNA为模板合成RNA B．核心酶能够在正确的位置起始转录，但效率比RNA聚合酶聚全酶低 C．核心酶能够催化以DNA为模板合成RNA，但不能在正确的位点起始转录 D．核心酶不能与DNA模板结合

单选题关于DNA构象，下列叙述正确的是( )。

单选题有的酶存在多种同工酶形式，这些同工酶所催化的反应______。

单选题关于乳酸循环的叙述，不正确的是

单选题有关DNA分子碱基组成的Chargaff规则揭示中，错误的是

单选题人体血浆载脂蛋白中，能激活LPL的是

单选题含有高能磷酸键的糖代谢中间产物是

单选题在真核细胞中，参与肽链的延长过程的辅因子是 A.eIF-2 B.eIF-3 C.eEF-1和eEF-2 D.RF E.eIF-4及eIF-5

单选题下列研究或发明中，哪一项未曾获得过诺贝尔奖?( ) A．朊病毒(Prion) B．PCR C．RNA干扰 D．克隆羊多莉