试题与答案

DNA的复制需要引物，其主要原因是[ ] A．可加快DNA的复制速度 B．引物可

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题型：选择题

题目：

DNA的复制需要引物，其主要原因是[ ]

A．可加快DNA的复制速度

B．引物可与DNA母链通过碱基互补配对结合

C．引物的5′端有助于DNA聚合酶延伸DNA链

D．DNA聚合酶只能从3′端延伸DNA链

答案：

答案：D

考点：多聚酶链式反应扩增DNA片段
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题型：阅读理解
阅读下面短文，把A-D填入文中空缺处（1－4），使短文内容完整正确，然后完成第5题。
       Nowadays, more and more young people are becoming vegetarians in most Western countries. They are thought of as vegetarians and they refused to eat meat, fish, eggs, cheese and milk.   1  . Some of them just don’t eat animal products such as milk, eggs, or yogurt, but some others are strict vegetarians and
they eat mainly fruit and vegetables. As we know, it is very important to have a balanced diet, especially
for the teenagers who are growing up.   2  . Well, each person chooses to become a vegetarian for
different reasons. The main reasons are they want to protect animals and they want to stay healthy.
       I decided to be a vegan when I was 15 years old. But as a vegetarian, I have had a difficult time in
getting the proper nutrition(营养).   3   . Of course, being a vegetarian isn’t for everyone.   4  .   
A. So why are they becoming vegetarians?
B. Most experts and doctors say that being a vegetarian is very healthy, but many people disagree.
C. So don’t get discouraged(泄气的) if you can’t give up hamburgers and meat dumplings!
D. There are many different types of vegetarians.
 
5. Which of the following is NOT true？
A. There are many vegetarians in most Western countries.
B. The main reason for being vegetarians is they don’t like eating meat.
C. Not everyone should be a vegetarian.
D. Keeping healthy is important to teenagers.
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