问题 选择题

定点突变是指通过多聚酶链式反应(PCR)等方法向目的DNA片段中引入所需变化(通常是有利的),包括碱基对的增添、缺失和替换等。定点突变能迅速,高效地改变DNA所表达的目的蛋白,从而影响生物性状,是基因研究工作中一种非常有用的手段。下列有关定点突变的叙述中不正确的是[ ]

A.定点突变可以利用DNA探针进行检测

B.定点突变引起的变异类型属于基因突变

C.应用定点突变技术可培育具有新性状的生物,形成新物种

D.应用定点突变技术可以研究蛋白质结构与功能的关系

答案

答案:C

阅读理解

阅读理解.

    "Well, we're in our new house. Let's get anew pet to get along with it, " Mrs Brown said to her husband.

    "That sounds like a pretty good idea," he answered, "Do you want to see the ads in the newspaper ?"

    "Let's go to the animal  shelter. Many pets there need homes. Since tomorrow is Saturday, we can

both  go , "she said.

    Next morning the Browns met Mr. Snow at the animal shelter. "We want to be sure that the pets here

go to good homes, "Mr Snow said, " So I need to ask you some questions. "

    After they talked for a while , the Browns decided to get a small dog. It wouldn't need a big house

or a  big yard. A small dog would bark(吠)and warn them if someone tried to break into their house.

After Mr. Snow gave the Browns a book on pet care, they chose one and wanted to take her home right

away.  But the animal, doctor hadn't checked her yet. So Mr. Snow told them to return on Sunday.

     On Sunday afternoon the Browns went to the animal shelter. The animal doctor said, "Shadow has

hadall of her shots(预防针). She will be healthy. " The Browns thanked the doctor and took Shadow

home.

1. From the reading we learn that __________ .

   A. the Browns have never had a pet before

   B. the Browns knew about Shadow from the newspaper

   C. Shadow is a small and healthy dog

   D. Mr. Brown didn't quite agree with his wife

2. The word"shelter"in the passage means ___________.

   A. a place to sell small dogs

   B. a place to keep homeless animals

   C. a place to study animals

   D. a place to sell books on pet care

3. Mr Snow asked the Browns some questions to ___________ .

   A. see if they had moved to a new house

   B. find out how rich the Browns were

   C. know where they'd keep their new pet

   D. make sure they'd take care of pets

4. The Browns thinks that a small dog __________ .

   A. doesn't need any room to keep

   B. can help them watch their house

   C. eats less food than a bigger one

   D. usually has a beautiful name

5. It's clear that __________ .

   A. Shadow will not be easy to get ill

   B. the Browns were not satisfied with Shadow

   C. Mr. Snow didn't check Shadow at all

   D. Shadow likes barking a lot

单项选择题