问题 多项选择题

在RNA的分离与纯化过程中,为了避免RNase对RNA的降解,应注意以下哪些问题()

A.要避免细胞外RNase的污染抑制其活性

B.操作时必须戴手套和口罩

C.所有的玻璃器皿与溶液均应以RNase的抑制剂DEPC进行处理

D.对各种材料和试剂均要进行严格的洗涤、纯化和高压消毒处理

E.在冰浴的条件下进行操作,也是减低RNase活性的有效措施

答案

参考答案:A, B, C, D, E

阅读理解

阅读理解。

     Marco Polo was born in Venice in 1254. He was the most famous foreigner to visit Asia during the

Middle Ages. He wrote a book about his travels. In his book he wrote all the things he saw and heard.

Many people in the west read the book, but few believed what Marco Polo said in the book. He told

stories about a lot of strange people and places. But at that time nobody knew these places and the

people.

     When Marco Polo was still very young, he decided to travel together with his father. It took them

more than three years to travel to China, later he became a friend of the Chinese emperor (皇帝) . He

learned to speak Chinese when he traveled around, and he talked to many people in Chinese. The

emperor liked him and made him a Chinese Official. At that time Marco Polo was only thirty years old.

After nearly seventeen years’ travel in the east, Marco and his father wanted to go back home.

     When Marco and his father arrived in Venice many years later, their family and friends saw them

again. They couldn’t believe their eyes because Marco and his farther were quite old. Marco Polo and

his father had been away for almost 25 years.

1. Marco Polo was                 foreigner who ________ to Asia during the Middle Ages.

2. Marco Polo wrote a famous book ________ “The Travels of Marco Polo". He told people _______

he saw and heard in the book.

3. Many people in the west read the book, but ________ believed ________.

4.It took Marco Polo and his father over three years to________.And Marco Polo worked as _______

in 1284.

5. Marco Polo and his father had been away ________. When they got back home in Venice, they were ________.

单项选择题