问题 填空题 案例分析题

大肠杆菌pUC118质粒的某限制酶唯一酶切序列,位于该质粒的lacZ基因中,lacZ基因中如果没有插入外源基因,lacZ基因便可表达出b-半乳糖苷酶,当培养基中含有IPTG和X-gal时,X-gal便会被b-半乳糖苷酶水解成蓝色,大肠杆菌将形成蓝色菌落;如果lacZ基因中插入了外源基因,带有pUC118质粒的大肠杆菌便不能表达b-半乳糖苷酶,培养基中的X-gal不会被水解成蓝色,大肠杆菌将形成白色菌落。pUC118还携带了氨苄青霉素抗性基因。下图是利用lacZ基因的插入失活筛选重组质粒示意图。据图回答下列问题:

作为受体大肠杆菌应()(填“含有”或“不含有”)氨苄青霉素抗性基因,以方便筛选已导入重组质粒的受体大肠杆菌。取用氯化钙溶液处理(增加其细胞壁的通透性)过的受体大肠杆菌,置于试管Ⅱ中,完成基因工程操作的()步骤(具体步骤)。如果受体细胞是植物细胞,则通过()转化作用将目的基因导入受体细胞,因为其Ti质粒中的T—DNA有()特点。

答案

参考答案:不含;目的基因导入受体细胞;农杆菌;可转移至受体细胞并且整合到受体细胞染色体DNA上

单项选择题
阅读理解

阅读理解。

     You know the sound of your heartbeat: lub-dub, lub-dub. In some people, there's an extra noise that the

blood makes as it flows through the heart. It sounds sort of like the noise of flowing water. This sound is

called a murmur.

     Just like kids, murmurs have grades. Grade l is the softest-sounding murmur, and Grade 6 is the loudest.

A murmur graded 4, 5, or 6 is so loud you can actually feel a rumbling from it under the skin if you put your

hand on the person's chest.

     Most murmurs don't mean anything is wrong. Doctors may call these "innocent", "functional", or "normal"

murmurs.

     One common type of normal murmur is Still's murmur, named for the doctor who first described it. This

murmur is most often heard in healthy children aged 3 to 7.

     A normal murmur can get louder when the blood flows faster through the heart, like when kids have a

fever or run around. That's because an increase in body temperature or activity makes the heart pump more

blood. When your temperature goes down, the murmur may get quieter or even disappear.

     It can be easier to hear heart murmurs in kids because they have less fat, muscle, and bone between the

murmur and the doctor's stethoscope (听诊器). Many normal murmurs become harder to hear as children

grow older, and some eventually disappear.

     Even though most murmurs do not mean anything is wrong, sometimes a heart problem can cause a

murmur. If your doctor thinks your heart murmur could be due to a heart problem, you will need to see a

pediatric cardiologist. This kind of doctor knows a lot about children's hearts.

1. What's the text mainly about?

A. Heart problems.

B. Heart murmurs.

C. Murmur types.

D. Murmur grades.

2. We can hear a kid's louder heart murmur when he has just _____.

A. woken up from a sound sleep

B. listened to some light music

C. played football for two hours

D. finished reading a storybook

3. This text is most probably taken from _____.

A. a science magazine

B. an experiment report

C. a hospital introduction

D. a medical advertisement

4. We can learn from the last paragraph that _____.

A. most heart murmurs do harm to kids' health

B. some heart murmurs can cause heart problems

C. doctors know what has led to low temperatures

D. a certain heart problem can cause a heart murmur