学科——青夏教育精英家教网—

科学家通过基因工程培育抗虫棉时，需要从苏云金芽孢杆菌中提取出抗虫基因，“放入”棉花的细胞中与棉花的DNA结合起来并发挥作用，请回答下列有关问题：
⑴ 从苏云金芽孢杆菌中切割抗虫基因所用的工具是______________，此工具主要存在于__________中，其特点是_________________________________________________。
⑵ 苏云金芽孢秆菌一个DNA分子上有许多基因，获得抗虫基因常采用的方法是“鸟枪法”。具体做法是：用______________将苏云金芽孢杆菌的__________切成许多片段，然后将这些片段____________________________，再通过_______________转入不同的受体细胞，让它们在各个受体细胞中大量______________，从中找出含有目的基因的细胞，再用一定的方法把__________________分离出来。
⑶ 进行基因操作一般要经过的四个步骤依次是________________________________、____________________________________、___________________________________、____________________________________。查看习题详情和答案>>

科学家利用动物做“________ ”，生产人类所需的某些物质，这就是________ 。查看习题详情和答案>>

1.科学家们认为世界上存有生命已有几百万年的历史了。

Scientists there has been life for years.

2.我们还没有在其他行星上发现生命。

We haven’t on other .

3.科学家们已经在宇宙中发现了许多别的星系。

Scientists many other in the .

4.弄清楚宇宙有多大是困难的。

It is hard large the is.

5.为什么没有人从别的行星上给我们发送信息呢？

Why has other planets us a message?

6.飞机已经到达了吗？

the plane ?

7.我听说你父母到北京出差去了。

I hear your father and mother Beijing .

8.你觉得这本小说怎么样？

the novel?

9.你在忙什么呢？

are you ?

10.请记住给我回信。

Please write me.

查看习题详情和答案>>

科I am a mother of three and have recently completed my college degree. The last class I had to take was sociology(社会学). The teacher was really great. The class was asked to go out and smile at three people.
I am a very       person and thought this would be a piece of cake. Soon after, my husband, youngest son and I went out to McDonald’s. We were standing in line, waiting to be       , when all of a sudden everyone around us began to     away, and then even my husband did.
As I turned around I smelled a terrible “dirty body” smell, and there standing behind me were two poor        men. As I looked down at the short gentleman, he was “     ”. His beautiful sky blue eyes were full of God’s Light as he searched for acceptance. He said, “Good day.” as he counted the few       he had been holding.
The young lady at the counter(柜台) asked him what they       . He said, “Coffee is all Miss.” because that was all they could afford. He just needed to be warm.
Then I really        it—the compulsion(冲动) was so great that I almost      out and hugged the little man with the blue eyes.
That is when I noticed all eyes in the restaurant were set on me, judging my every action. I smiled and asked the young lady behind the counter to give        two more breakfast meals on two plates.
I then picked up the plates and walked around the counter to the             that the men had chosen as a resting place. I put the plates on the table and laid my hand on the blue-eyed gentleman’s        hand. He looked up at me, with tears in his eyes, and said, “Thank you.”
I graduated with one of the biggest lessons I would ever learn：acceptance without condition.
小题1:

试题分类