单选题Did you ever have someone's name on the tip of your tongue and yet you were unable to recall it? (1) this happens again, do no (2) to recall it. Do something (3) for a couple of minutes, (4) the name may come into your head. The name is there since you have met (5) person and his name. It (6) has to be dug out. The initial effort to recall (7) the mind for operation, but it is the subconscious (8) that go to work to dig up a (9) memory. Forcing yourself to recall (10) never helps because it doesn't (11) your memory；it only tightens it. Students find the preparatory method help (12) examinations. They read over the questions (13) trying to answer any of them. (14) they answer first the ones (15) which they are most confident. Meanwhile, deeper mental activities in the subconscious mind are taking (16) ; work is being done on the (17) difficult questions. By the time the easier questions are answered, answers (18) the more difficult ones will usually begin to (19) into consciousness. It is often (20) a question of waiting for recall to come to the memory.

单选题以下多肽序列中，哪个最有可能形成α螺旋结构______。

单选题维生素D的主要生化作用是

单选题在真核生物细胞中tRNA的转录是由( )。

单选题下列有关三羧酸循环的叙述中正确的是

单选题下述氨基酸能直接脱去氨基变成α-酮酸的为(　　　)

单选题亚二倍体是指( )。

单选题有关核酶的哪种表述是不正确的( ) A．具有引导序列 B．具有锤头状结构 C．切断目的mRNA而自身没有消耗 D．核酶两端的引导序列与靶分子序列互补 E．使mRNA不能转录

单选题大鼠出生后饲以去脂膳食，结果将引起下列哪种脂质缺乏( )(1999年)

单选题脑中氨的主要去路

单选题为了分析小鼠肝脏组织中某一特定基因在不同条件下表达水平的变化，可能采用的实验手段是______。 A．Southern杂交 B．Nonhem杂交 C．酵母双杂交 D．荧光原位杂交

单选题蛋白质生物合成过程中。肽链的延长与下列哪种因素无关?

单选题EST序列本质上是______。 A．基因组DNA B．cDNA序列 C．mRNA序列D．多肽序列

单选题经分解代谢可产生一碳单位的氨基酸是( )(2011年)

单选题A．逆转录B．中心法则C．复制D．翻译E．转录

单选题以下哪一项不是在果蝇中发现的转座子或逆转座子：

单选题断裂基因的外显子是指：

单选题严重肝病时，男性出现乳房发育、蜘蛛痣的原因是 A.雌激素分泌增加 B.雄激素分泌减少 C.雌激素灭活减少 D.雄激素灭活过多 E.雌激素灭活过多

单选题活化后的氨基酸才能与tRNA结合，每个氨基酸的活化过程需要消耗几个高能磷酸键______ A.1 B.2 C.3 D.4 E.5

单选题3种等电点不同的蛋白质：甲蛋白等电点为6.1，乙蛋白为4.3，丙蛋白为5.7。在负极点样后再电泳30分钟，请问哪种蛋白泳动的距离最远( ) A．甲蛋白 B．乙蛋白 C．丙蛋白 D．距离无差别 E．不一定