问题 问答题

核内小RNA——snRNA是什么试举例说明其作用。

答案

参考答案:真核生物的细胞中,有许多100~300碱基的小分子RNA,每个细胞含有105~106个分子,或者是由RNA聚合酶Ⅲ转录,或者是由RNA聚合酶Ⅱ转录。在核中的这种小分子RNA称为snRNA。在各种snRNA之间具有序列的共同性。一般情况下,它们都是以核蛋白的形式存在,即RNP。snRNA在细胞中主要是与mRNA前体组装形成拼接体参与mRNA前体的拼接。U1 snRNA的5’端序列能够与mRNA前体的两个拼接点序列互补,U1 snRNP通过其RNA识别5’端拼接点序列并与之结合;U2snRNP通过其RNA识别并结合分支点;U5 snRNP通过其70 kDa辅助蛋白质结合于3’拼接点内部的富含嘧啶的共有序列。

阅读理解

阅读理解。

     Steve Ballmer is always exciting, as he was this time in front of over 2,000 students from Qinghua

University and Beijing University.

     Ballmer, president (总裁) of Microsoft Corp., received a warm welcome at Qinghua University when he

gave a talk on the next generation (一代) of the Internet on September 19th. He came to China last week for

a two-day visit, during which he slept only four hours and had many meetings with government officials (政府官员) and men of business. After all those business matters, he came to Qinghua and was asked thousands

of questions from the excited students.

     Ballmer, who joined Microsoft in 1980, is the first business manager hired (聘用) by Bill Gates, a

schoolmate of Ballmer at Harvard. Gates first dropped out of school to start Microsoft and Ballmer was still

studying, but he also gave up his studies and joined Bill Gates' five-year-old Microsoft in 1980.

     In his talk to the students, Ballmer described what the Internet will bring to their life. He said there are

several hundred Qinghua graduates now working or being trained at Microsoft both in China and in the US.

He also warned the students not to drop out of school and follow the examples of Bill Gates and himself.

1. Ballmer gave a talk on ___________ at Qinghua.

A. the future of the Internet

B. how to use the software made in his company

C. what computers will bring to universities

D. his own experience from Harvard to Microsoft

2. It seemed that Ballmer came to China mainly ___________.

A. to meet some government officials

B. to give a talk at Qinghua University

C. to manage business matters

D. to visit places of interest

3. He encouraged Chinese students ___________.

A. to work for Microsoft in China or in America

B. to follow the examples of Bill Gates and himself

C. to work on software

D. to go on and finish their college education

4. From the passage we know Steve Ballmer ___________.

A. graduated from Harvard University

B. asked the students a lot of questions

C. is president of Microsoft Corp

D. started Microsoft Corp. in 1980

选择题