问题 问答题 简答题

假定有一个DNA分子,在它的一条链上有一个长达5000个核苷酸、两端为3’-OH和5’-P基团的缺口。如果在离体条件下把DNA聚合酶加到这个分子中去(还包括合成DNA所需要的其他物质),那么填补这个缺口将是整条片段还是一些短片段如果这个缺口在体内填补,又该是怎样的片段。

答案

参考答案:

缺口将由一条片段填补,只要缺口的一端有3’-OH基团就不会形成许多短片段。

阅读理解

Many people go to school for an education. They learn languages, history, politics, geography, physics, chemistry and mathematics. Others go to school to learn a skill so that they can make a living.

School education is very important and useful. Yet, no one can learn everything from school. A teacher, no matter how much he knows, can not teach his students everything they want to know. The teacher’s job is to show his students how to learn. He teaches them how to read and how to think. So, much more is to be learned outside school by the students themselves.

It is always more important to know how to study by oneself than to memorize some facts or a formula(公式). It is actually quite easy to learn a certain fact in history or a formula in math. But it is very difficult to use a formula in working out a math problem.

Great scientists before us didn’t get everything from school. Their teachers only showed them the way. Edison didn’t even finish primary school. But they were all so successful. They invented so many things for mankind. The reason for their success is that they knew how to study. They read books that were not taught at school. They would ask many questions as they read. They did thousands of experiments. They worked hard all their lives, wasting not a single moment. Above all, they knew how to use their brain.

小题1: People go to school to _________.

A.learn several subjects

B.make a living

C.get an education

D.learn from teachers小题2: According to the passage, the most important thing a teacher should do is _________.

A.to teacher his students everything he knows

B.to teach the students how to think

C.to know everything they want to know

D.to teach the students how to work out a math problem小题3:To work out a math problem, you need to know _________.

A.only a certain formula

B.a certain fact

C.some facts

D.the way to solve it小题4:Why were many scientists so successful?

A.They received good education.

B.They were very clever.

C.They knew how to learn.

D.They learned lots of facts and formulas.小题5: How did great scientists study?

A.They read a lot of books and asked many questions while reading.

B.They did thousands of experiments.

C.They always worked hard and never wasted time.

D.All of the above.

单项选择题