问题 单项选择题

下列对DNA克隆操作的描述哪一项是错误的

A.限制性内切酶在特定的位置上切割质粒和供体DNA分子

B.载体DNA和供体DNA在连接酶的作用下末端相连形成重组DNA

C.除质粒外,λ噬菌体可作为重组 DNA的载体

D.筛选含重组DNA的细菌通常可根据载体对抗生素的抗性来进行

E.以质粒为载体构建的重组DNA分子引入宿主细胞时需与宿主 DNA结合

答案

参考答案:E

解析: DNA克隆是指应用酶学的方法,在体外将各种不同来源的DNA与载体DNA连接成具有自我复制能力的DNA分子,进而通过转化或转染宿主细胞,筛选出含有目的基因的转化子,再进行扩增、提取获得大量同一的DNA分子。故E项错误。

阅读理解

When you are feeling unhappy or forget how great you are, these are six ways to make you feel good about yourself.

1) Look in the mirror and say to yourself, “I am a special person and there’s no one in the world like me. I can do anything!” It may not sound so good, but it really works!

2) Do something nice for someone. Helping others always makes you feel good.

3) Smile! Be friendly to people you meet. Look for the good things in your friends and family.

4) Learn something new! Have you always wanted to decorate your own room or learn how to swim? New challenges are fun and give you a sense of accomplishment when you have finished.

5) Read and start a diary. Turn off the TV and let your imagination fly! Write down your thoughts, dreams or anything you want! Writing always helps to express your feelings.

6) Stay with your family. We all need our family time. Talk with your Mum or Dad or maybe even your cousin.

小题1:This passage may be taken from         .

A.a science book

B.a story book

C.a magazine

D.school rules小题2:According to the passage, when you are helping others, you will         .

A.be special

B.be sure

C.feel nice

D.be remembered小题3:What do the underlined words in 4) “a sense of accomplishment” mean?

A.成就感

B.忧伤感

C.挫折感

D.信任感小题4:Which of the following should you say “NO”  when you are unhappy?

A.You should always look for the good things of others.

B.Stay alone at home as much as possible.

C.Learn something new and go for it!

D.Keep a diary to express your feelings.小题5:The best title for the passage is         .

A.Do Your Best

B.Six Ways to Feel Good about Yourself

C.It’s Never too Late to Learn

D.Always Smile to Yourself

单项选择题