问题 实验题

有些微生物含有纤维素酶,通过对这些微生物的研究和应用,使人们能够利用秸秆等废弃物生产酒精,用纤维素酶处理服装面料等。纤维素酶可以通过微生物进行发酵生产。为了提高酶的产量,请你设计一个实验,利用诱变育种的方法,获得产生纤维素酶较多的菌株。

(1)写出实验步骤:

①.___________________________________;

②.___________________________________;

③.___________________________________;

④.___________________________________。

(2)预期实验结果及结论:______________________________。

答案

(1)实验步骤:

①.将培养好的生产菌株分成两组,一组用一定剂量的诱变剂处理,另一组不处理作为对照组

②.制备碳源为纤维素的菌体培养基若干

③.把诱变组的大量菌株接种到多个含有纤维素的固体培养基上,同时接种对照组(未处理的菌株)。把它们置于相同的条件下培养

④.一段时间后,取两组培养基,用刚果红染色,观察并记录菌落周围透明圈的大小情况

(2)预期实验结果及结论:a.诱变组中有些菌落周围的透明圈与对照组相比较大,说明诱变育种获得了高纤维素酶产量的菌种。b.诱变组中的菌落周围的透明圈与对照组相比大小相同,说明诱变育种没有菌株发生变化。c.诱变组中有些菌落周围的透明圈与对照组相比较小,说明诱变育种获得了低纤维素酶产量的菌种。

阅读理解

阅读理解。

     Last Friday, a Tibetan (藏族的) postman became the first woman postal worker to give a speech at

the World Postal Meeting in Bern, the capital of Switzerland. She was Nima Lamu, a postwoman of Yunling

Post office, Yunnan Province.

     She said, "I had to cross the Lancang River along a steel wire. My younger brother nearly died in the

river before. I felt so afraid when I was asked for the first time to cross the river. But when I reached the

other side, I found that I was flying."

     Her area is locked in (封闭) two snowy mountains and three big rivers. She said,":What worries me most

is the snakes on the way. Sometimes, I throw little stones toward them and I often tell my self 'Keep going'."

     Ten years ago, it took Nima five days to finish each week's mail. She had to face snowstorms, floods,

snakes and loneliness on her 350-kilometer journey. Nima said, "The situation has developed a lot these years.

Now we have a bridge that was built across the Lancang River in 2006."

     Nima never dreamed she would become famous one day when she first look up her job, 12 years ago.

Changes have been seen in recent years as more tourists visit Nima's hometown. But one thing remains

unchanged: she is still the carrier of the villagers' hopes and dreams.

1. Nima was invited to the meeting in Bern because she was _________.

A. the only Tibetan postman in China

B. the first postwoman in the world

C. doing a hard job as a postwoman

D. making her village famous overnight

2. What happened to her brother according to Nima Lamu?

A. he once fell into the river.

B. He was killed by a snake.

C. He died when swimming in the river.

D. He got hurt when building the bridge.

3. Which picture is TRUE about Nima's crossing the river ten years ago?

4. What will Nima do if she finds a snake on the way?

A. Kill it with stones.

B. Keep it off and go on.

C. Throw it away and leave.

D. turn around and run.

5. What is RTUE about Nima?

A. She is building a bridge across the Lancang River.

B. She has realized all the villagers' dreams.

C. She got her job as a post woman before 2000.

D. She doesn't need to do her work now.

单项选择题