问题 问答题

根据实验回答下列问题:

(1)DNA的粗提取实验中可以选用鸡血做实验材料,是否可用羊、牛、马的血做实验材料?

(2)在加冷酒精提取丝状物过程中,要用玻璃棒沿一个方向缓慢搅拌溶液,为什么?

(3)从上清液中析出的丝状物是否能代表DNA分子?

答案

(1)不能用,因为用它们做实验材料很难提取到DNA。

(2)有利于DNA析出,防止DNA分子断裂。

(3)不是,它是由很多DNA分子聚在一起形成的聚合体。

阅读理解

What is green food? Do you enjoy green food every day? The concept of “green food” was first suggested by the Department of the Ministry of Agriculture in 1990.

Green symbolizes life, health and energy. Nowadays, people demand healthy and fresh food. Having enough food to eat is only a basic requirement, and they need more than this. They want to enjoy unpolluted, safe and nutritious food and eat comfortably. So the government does this through a set of “from the land to the dinner table” quality controls. It requires to change China’s traditional agricultural structures and ensure the food of high quality.

Safe vegetables refers to products without substances harmful to humans. Growing such vegetables requires no strong poisons, thus guaranteeing vegetables fresh and clean. There are strict regulations in place for even applying fertilizer(肥料). The examination of vegetables should reach the state food hygiene(卫生) standard. The following conditions for green food are regulated by the China Green Food Development Center. Firstly, products or raw materials must reach the green ecological environment standard set by the Ministry of Agriculture. Secondly, crop planting, livestock raising, fish breeding and food processing must follow green food operating procedures set by the Ministry. Products must be up to the green food hygiene standard. External packing must be pasted with national standard universal labels, special green food packing decoration and tag regulations.

However, by now, our goal hasn’t been completely realized. When you return home with a full basket, you are still worried about whether what you have bought is green and healthy. Indeed, for the sake of our health, we still have a long way to go.

小题1: According to the passage, we know that green food __________.

A.means the color of food is green

B.mainly refers to green vegetables

C.doesn’t need to be fertilized

D.is examined by a series of standards小题2:Which of the following isn’t the required standard green food must reach?

A.Green food must not cause ecological destruction.

B.Green food should agree with green food operating procedures.

C.Green food itself should be labeled with special packing decoration.

D.Green food should meet the green food hygiene standard.小题3: According to the passage, we know the Ministry of Agriculture is a department ____.

A.which governs agriculture

B.which sells food and vegetables

C.which plants green food

D.which examines food standards小题4:The best title for this passage probably is ___________.

A.Green food and health

B.The green food project

C.The future of green food

D.The regulations of green food

单项选择题