英语听力教程5 Unit 3 Part 3答案及文本

Unit 3 Genetics ABC

Part III

A

Questions:

1. What are the two functions of DNA?

a. protein synthesis

b. maintain constant/genetic information

2. How does DNA perform the first function mentioned in the passage? Complete the chart below. DNA molecule (makes) RNA

leaves the nucleus

read instructions in the ribosomes

form proteins

3. How does DNA perform the second function mentioned in the passage?

duplication/in cellular division

Why do we have different colors of skin, hair and eyes? Why do beings so different from one another exist? DNA or deoxyribonucleic acid, a molecule found in the nucleus of all cells is responsible for this tremendous variety. George Mendel was the first person to investigate genetic inheritance. He deduced that characteristics are inherited through physical units which he called genes. Nowadays we know that all cells contain chromosomes which are made up of DNA molecules. Sugars and phosphates form the backbone of each chain and they are united through their basis in a determined fashion. These two chains curl around themselves forming a double spiral. DNA has a specific role to play in the cell, that of protein synthesis. To make it, the DNA molecule makes an almost exact copy of itself called RNA. The copy leaves the nucleus and reads the instructions in the ribosomes. It's here where proteins, so essential to living beings, are formed, since they are responsible for controlling the many chemical reactions which keep us alive. The other important mission of DNA is maintaining constant the genetic information of the species during thousands of years through its duplication during cellular division.

C

1. How many men in Britain snore?

Six percent of all men.

2. How many men in Britain suffer from sleep apnoea?

Two percent of all men.

3, What are the symptoms of those people who suffer from sleep apnoea?

a. They snore loudly.

b. They can stop breathing for more than ten seconds as much as ten times an hour.

4. What may sleep apnoea lead to?

a. Disturbed sleep.

b. A risk of depression.

c. The danger of falling asleep while driving.

5. What might cause sleep apnoea?

a. Having a short jaw.

b. Being overweight.

c. Some genetic element

Doctors in Britain think they may have discovered why some people snore when sleeping. Based on a study of eight families, in which one or more members have a serious snoring problem, the doctors say that snoring could be genetically inherited. If that theory is correct, it could explain why some people suffer more than others from the condition.

It's estimated that six percent of all men in Britain snore but two percent suffer from what's known as sleep apnoea. Those with the condition snore very loudly and can stop breathing for more than ten seconds as much as ten times an hour. Sufferers are often unaware of their condition, but it does lead to disturbed sleep, a risk of depression and even the danger of falling asleep while driving.

It's thought it could be caused by having either a short jaw or by being overweight. But doctors of the Royal Halemshire Hospital in Sheffield believe there may be a genetic element. They are studying eight families where one or more members have the condition. So far they've found evidence that sleep apnoea can run in families. The next step is for blood samples to be taken to determine if a gene is involved. If it is, it could help diagnose people with the condition earlier.