问题 填空题 案例分析题

现有甲、乙两个烟草品种(2n=48),其基因型分别为aaBB和AAbb,这两对基因位于非同源染色体上,且在光照强度大于800勒克司时,都不能生长,这是由于它们中的一对隐性纯合基因(aa或bb)作用的结果。取甲乙两品种的花粉分别培养成植株,将它们的叶肉细胞制成原生质体,并将两者相混,使之融合,诱导产生细胞团。然后,放到大于800勒克司光照下培养,结果有的细胞团不分化,有的能分化发育成植株。请回答下列问题:

将叶肉细胞制成原生质体时,使用()破除细胞壁。

答案

参考答案:纤维素酶

阅读理解

阅读理解。

     Who hasn't found themselves reaching for the closest food available when they're tired and stressed?

More and more research is proving that this isn't all in our mind. Some foods really do lead to a change

in our moods (心情).

     Carbohydrate (碳水化合物) that calm

     This is how some people medicate themselves with food-by reaching for cookies or pasta (面食)

whenever they're upset. Unfortunately, it doesn't always work. You must eat a meal consisting of 100%

carbohydrate, on an empty stomach, to obtain the serotonin (血清素) increase so that you have a good

mood.

     To get the wished-for effect, you must not eat anything for four hours and then eat at least 30 grams

of straight carbohydrate. Dry cereal (麦片), a piece of bread with jam, or a potato should do the trick.

     Protein (蛋白质) for Power

     Of course, sometimes we don't need to be calm and sleepy. Sometimes we need a great deal of mental

concentration, so this is when it's important to mix protein and carbohydrate. The protein will prevent the

tryptophan (色氨酸) from flooding your brain, and the rise in serotonin won't occur.

     Why dessert makes up Happy

     Fat and sugar cause the brain to let go endorphins (内啡肽), which send pleasure signals throughout

the body. This would be fine, except humans are not particularly good at stopping at one cookie or cake.

     You can also satisfy your sweet tooth by choosing fruit for dessert.

     Timing your meals for energy

     Blood sugar drops after four hours of going without food, causing a decrease in energy. Eating usually

fixes this within 20 to 30 minutes, but don't suppose that eating more will cause a faster increase in energy.

     When you eat has as much of an effect on your mood as what you eat. If you regularly go for a long

period of time between meals, rethink your schedule and plan ahead.

1. The underlined phrase in the third paragraph means _____.

A. be extremely smart

B. intend to cheat someone

C. bring about the desired result

D. do something to amuse people

2. The function of protein is _____.

A. to help you keep calm and sleepy

B. to make you feel energetic

C. to lead you to slowness

D. to increase serotonin in your brain

3. We can infer from the last two parts that _____.

A. fat and sugar can greatly help people feel happy

B. we humans tend to eat lots of cookies and cakes

C. the more we eat, the faster we will gain energy

D. what we eat is more important than when we eat

4. The main idea of the passage is _____.

A. eating for a better mood

B. eating to make you calm

C. eating for more protein

D. eating to make us strong

单项选择题 A1型题