单选题决定氨基酰-tRNA进入核糖体A位的结构是 A.tRNA反密码子 B.mRNA密码子 C.核糖体 D.转肽酶 E.EF-T或EF-1、2

单选题A.12.5molATPB.15molATPC.10molATPD.32molATP

单选题下列物质在PCR中不能作为模板的是 A.RNA B.单链DNA C.cDNA D.蛋白质 E.双链DNA

单选题下面RNA中分子量最小的是

单选题1条染色体发生断裂后，断段插入其同源染色体中，结果造成( )。

单选题呼吸链中的递氢体为(　　　)

单选题A.UCAB.AUGC.UAAD.GCU

单选题A．蚕豆病B．苯丙酮尿症C．帕金森病D．镰刀型红细胞贫血症 (2012年)

单选题已知有三个位点是连锁的，D和E相距20个图距单位，E和F相距20个图距单位，又知三位点的顺序是DEF。用杂交DDEEFF×ddeeff的子代进行测交，就表型分类，发现测交子代中，有2%的DdeeFf和2%的ddEeff，根据这些资料，此区段的并发系数______ A.1 B.0.5 C.0 D.已给的资料可计算并发系数，但上述答案都不对 E.不能计算并发系数

单选题肾上腺激素是通过______起作用的。

单选题A．磷脂酸B．CDP-甘油二酯C．二者都是D．二者都不是 (2000年)

单选题A．α-螺旋B．左手双螺旋C．右手双螺旋D．三叶草E．倒L型

单选题临床上出现黄疸时，尿中可检出的化合物是 A.胆红素 B.尿胆素原 C.尿胆素 D.尿胆红素 E.粪胆素

单选题催化聚合酶链式反应的酶是______ A.DNA连接酶 B.反转录酶 C.末端转移酶 D.DNA聚合酶I E.TaqDNA聚合酶

单选题In old days, when a glimpse of stocking was looked upon as something far too shocking to distract the serious work of an office, secretaries were men. Then came the first World War and the male secretaries were replaced by women. A man's secretary became his personal servant, charged with remembering his wife's birthday and buying her presents; taking his suits to the dry cleaners; telling lies on the telephone to keep people he did not wish to speak to at bay and, of course, typing and filing and taking shorthand. Now all this may be changing again. The microchip and high technology is sweeping the British office, taking with it much of the routine clerical work that secretaries did. "Once office technology takes over generally, the status of the job will rise again because it will involve only the high-powered work-and then men will want to do it again." That was said by one of the executives(male) of one of the biggest secretarial agencies in this country. What he has predicted is already under way in the US. One girl described to me a recent temporary job placing men in secretarial jobs in San Francisco. She noted that all the men she dealt with appeared to be gay so possibly that is just a new twist to the old story. Over here, though, there are men coming onto the job market as secretaries. Classically, girls have learned shorthand and typing and gone into a company to seek their fortune from the bottom——and that's what happened to John Bowman. Although he joined a national grocery chain as secretary to its first woman senior manager, he has since been promoted to an administration job. "I filled in the application form and said I could do audio/typing, and in fact I was the only applicant. The girls were reluctant to work for this young, glamorous new woman with all this power in the firm. " "I did typing at school, and then a commercial course. I just thought it would be useful finding a job. I never got any funny treatment from the girls, though I admit I've never met another male secretary. But then I joined the Post Office as a clerk and carelessly played with the typewriter, and wrote letters, and thought that after all secretaries were getting a good ￡1,000 a year more than clerks like me. There was a shortage at that time, you see. " "It was simpler working for a woman than for a man. I found she made decisions, she told everybody what she thought, and there was none of that stuff' ring this number for me dear, which men go in for." "Don't forget, we were a team—that's how I about it—not boss and servant but two people doing different things for the same purpose." Once high technology has made the job of secretary less routine, will there be male takeover? Men should beware of thinking that they can walk right into the better jobs. There are a lot of women secretaries who will do the job as well as they because they are as efficient and well trained to cope with word processors and computers, and men.

单选题能编码具有酪氨酸蛋白激酶活性的癌基因是

单选题磷酸化时活性增高

单选题有一糖蛋白经测定其含氮量为0.5mol，那么其蛋白质含量为多少?______

单选题 下列病毒中属双链RNA病毒的是 A、流感病毒 B、乙型脑炎病毒 C、麻疹病毒 D、疤疹病毒 E、轮状病毒

单选题白喉毒素抑制的过程是 A.翻译起始过程 B.翻译延长过程 C.翻译终止过程 D.DNA拓扑异构酶反应 E.核酶反应