题目内容
Heredity （遗传） is not the only thing that influences our color. Where we live and how we live after we are born are important too. For instance, our genes influence how fat or thin we are. But our weight depends mainly upon how much we eat and how much exercise we get. In the same way, our skin color depends to a large extent upon how much sunshine we get.
When summer arrives and light-colored people go to the beaches, some will tan darkly, some will tan lightly and few will not tan at all. Each one is born with a different ability to tan, but the differences do not appear until the conditions are right An outdoor man will soon become pale if he changes to an indoor job, while a desk clerk will take on tan after a short vacation in the sun. Sometimes people decide that being tanned is better than being pale. Sometimes they decide the opposite.
Centuries ago, most of the people in Europe were peasants and they had to work in the fields all day. Noblemen, on the other hand, did not have to work. They stayed indoors and remained pale. You could always tell a nobleman from a peasant because a peasant had a tan. As a result, noblewomen did their best to keep skins as light as possible. A skin so pale was considered a mark
of great beauty and nobleness.
During the Industrial Revolution things changed. Farmers left their fields and went to work in factories, mines and mills. Working for long hours in dimly-lit factories and mines made their skins pale. Wealthy people, however, could afford to travel to sunny countries. They had the leisure （空闲）to lie around on the beaches and get tan. Having a tan became a sign of wealth.
In Western Europe and North America pale skin is no longer desirable. Instead of bleaching themselves white with lemon juice, many women spend their time under a sun-lamp. The desire for a quick tan has led to the invention of pills and lotions （化妆水）that darken the skin artificially without exposure to sunlight These pills and lotions can be bought by anyone at any drugstore. A rich man can spend hundreds of dollars on a vacation in the sunny West Indies and get his suntan there. But his lowest-paid clerk can have what looks like the same tan out of a bottle for a few cents.
1．Besides genes, our skin color has much to do with ______.
A．exercise B．sunshine C．food D．weight
2．Centuries ago in Europe, it was considered of great beauty to have ______.
A．pale skin B．light-colored skin
C．dark-colored skin D．a suntan
3．During the Industrial Revolution people began to like to have a tan because it was a sign of
.
A．good health B．great strength C．wealth D．youth
4．Pills and lotions have been invented in Western Europe and North America .
A．to make people look wealthy B．to smooth people’s skin
C．to help people to have a quick tan D．to protect people from suntan
5．What does the passage mainly tell us?
A．Noblemen centuries ago did not like traveling.
B．Attitudes towards the color of skin change with time.
C．Exposure to sunlight is the only thing that determines skin color.
D．Having a tan is considered a sign of wealth nowadays in North America.
BACCB
Have you ever heard a news reporter talk about DNA? Reporters talk about DNA found at the scene of a crime. They talk about police finding DNA “fingerprints.” Police sometimes use DNA as a clue to find out who committed the crime.
DNA is a substance（物质） that makes up genes. Everything alive has genes. Plans have genes. Animals have genes. Yo
u have genes.
Genes are the basic units of heredity（遗传）. Heredity means all the characteristics you inherit from your parents. You get your genes from your parents. You inherit half of your genes from your mother. You inherit half of your genes from your father.
Genes are a kind of code. A tree’s genes tell w
hat shape its leaves will be. A cat’s genes tell what color its fur will be. Your genes tell what color your eyes will be. Your genes tell what color your hair will be. Everything about you co
mes from the code in your genes.
Genes line up on strands（链） called chromosomes（染色体） in cells. Everything alive is made up of cells. Chromosomes are in the center, or nucleus, of cells.
Different parts of you are made of different kinds of cells. Your muscles are made of muscle celIs. Your skin is made of skin cells. The code in your genes tells your body to make different kinds of cells. The genes in each cell tell the cell how to work. They tell the cell when to make new copies of itself.
An Austrian monk named Gregor Mendel first saw inherited patterns in pea plants. He experimented with pea plants in the 1860s. One of the things, or traits（特质）， Mendel studied was what makes some pea plants tall and some short. He said that the traits must come from units of heredity passed from the parent plants. These units were later called genes.
In the mid-1900s, scientists discovered that genes are made of DNA. In the 1970s, scientists learned how to change DNA with genetic engineering. Scientists also learned that problems with certain genes cause diseases. Muscular dystrophy, cystic fibrosis, and hemophilia are some genetic diseases-diseases caused by problems in genes. Today, scientists are looking for ways to cure genetic diseases by changing genes through a process called gene therapy.
【小题1】 What is DNA?
| A．DNA is a kind of gene. |
| B．DNA is a substance that makes up genes. |
| C．DNA is the basic unit of heredity. |
| D．DNA is a measure to protect crime. |
| A．Plants, animals and human beings have the same genes. |
| B．Half people inherit all genes from their mother, others from their father. |
| C．Genes decide the trees shapes, the cats’ fur color and our eyes’ color as well. |
| D．Genes will give you a code when you need them. |
| A．Genes lining up on strands called chromosomes are in the center of cells. |
| B．Genes hide in everything alive in your body. |
| C．Genes can be nowhere but in your mind, controlling all your actions. |
| D．Genes travel in your body and help cope skin, muscle, and eyes. |
| A．first saw inherited patterns in people |
| B．was interested in why plants were different |
| C．first called the units of heredity from parents genes |
| D．was the first who discovered genes |
| A．scientists were less intelligent than monks in 1900s |
| B．some genes are bad and can cause diseases |
| C．we don’t need to worry about genetic diseases any longer |
| D．the discovery of genes may be of great help in our daily life |
Researchers at Sweden’s KTH Royal Institute of Technology say they have found further proof that the wolf ancestors of today’s dogs can be from southern East Asia -- findings that are contrary to theories placing the birth place in the Middle East. Dr Peter Savolainen, KTH researcher in evolutionary genetics, says a new study released Nov. 23 confirms that an Asian region south of the Yangtze River was the principal and probably the only region where wolves were domesticated（驯化）by humans.
Research data show clearly that dogs are descended from wolves, but there’s never been scientific agreement on where in the world the domestication process began. “Our analysis of Y-chromosomal（染色体）DNA now confirms that wolves were first domesticated in Asia south of Yangtze River -- we call it the ASY region -- in southern China or Southeast Asia,” Savolainen says.
The Y data supports previous evidence from mitochondrial（线粒体）DNA. “Taken together, the two studies provide very strong evidence that dogs appeared first in the ASY region,” Savolainen says.
Archaeological data and a genetic study recently published in Nature suggest that dogs originate from the Middle East. But Savolainen rejects that view. “Because none of these studies included samples from the ASY region, evidence from ASY has been overlooked,” he says.
Peter Savolainen and PhD student Mattias Oskarsson worked with Chinese colleagues to analyse DNA from male dogs around the world. Their study was published in the scientific journal Heredity.
Approximately half of the gene pool was universally shared everywhere in the world, while only the ASY region had the entire range of genetic diversity. “This shows that gene pools in all other regions of the world most probably originate from the ASY region,” Savolainen says.
“Our results confirm that Asia south of the Yangtze River was the most important -- and probably the only -- region for wolf domestication, and that a large number of wolves were domesticated,” says Savolainen.
In separate research published recently in Ecology and Evolution, Savolainen, PhD student Arman Ardalan and Iranian and Turkish scientists conducted a comprehensive study of mitochondrial DNA, with a particular focus on the Middle East. Because mitochondrial DNA is inherited only from the mother in most species, it is especially useful in studying evolutionary relationships.
“Since other studies have indicated that wolves were domesticated in the Middle East, we wanted to be sure nothing had been missed. We find no signs whatsoever that dogs originated there,” says Savolainen.
In their studies, the researchers also found minor genetic contributions from crossbreeding between dogs and wolves in other geographic regions, including the Middle East.
“This subsequent dog/wolf hybridisation（混合淡化技术）contributed only modestly to the dog gene pool,” Savolainen explains.
【小题1】What does Dr. Peter Savolainen believe?
A. Dogs’ ancestors came from the Middle East.
B. Wolves were probably first trained to work for humans in the ASY region.
C. Analysis of Y-chromosomal DNA should be combined with mitochondrial DNA.
D. Samples of the previous studies are enough to support the conclusion.
【小题2】We can learn from the passage that _______.
| A．there is a universal agreement on the place of first domestication |
| B．data from ASY may highlight where dogs came from |
| C．Dr. Savolainen’s research mainly focuses on the Middle East |
| D．the dog/wolf hybridization makes up most of the dog gene pool |
| A．It is only used in studying evolutionary relationships. |
| B．It alone can provide hard evidence for Savolainen’s research. |
| C．It is the most useful in finding out the birth place of dogs. |
| D．It comes from the mother of most animals and plants. |
Directions: Read the following text and choose the most suitable heading from A – F for each paragraph. There is one extra heading which you do not need.
E．Choosing subjects to study． F．Other characteristics typical of super．young people |
How They Stay Young
76.________________
When Dr David Weeks，a clinical neuro-psychologist at the Royal Edinburgh Hospital in Scotland．wanted to look into the secrets of eternal（永久的） youth ，he advertised for subjects who looked younger than their age．An independent panel examined photographs of respondents，and selected 3,500 people who looked on average l2 to 14 years younger than their actual age to take part in the study．
77．________________
These subjects were studied for eight years．The main aim of the study was to discover whether environment or heredity had more effect on the ageing process．The conclusion was that genetic programming is the main factor．But the study also showed that avoiding stress can slow down the ageing process．
78．________________
Stress seems to have an immediate effect on appearance．A separate study of middle-aged women showed that women suffering form serious stress looked older in just a few months．Yet when the problem causing the stress was removed，they very quickly looked younger．
79．________________
Here is a list of the factors that Dr．Weeks found that allowed his subjects to lead less stressful lives than others．First，they tend to have happy relationships with their partners．These relationships are based on trust and empathy，and provide security and comfort when dealing with stressful problems．Secondly，they tended to avoid sources of hostility instead of allowing them to make them angry．
80．________________
Next, they seem to have a good sense of humor．They like to have fun，and are enthusiastically involved in a variety of hobbies．They also seemed less willing to conform to others’ ideas．They prefer to think for themselves．They tend to have a good attitude towards health and exercise as well．They avoid the sun，do not smoke, and eat a healthy diet．
So these are the secrets of the “ super-young”：a loving relationship．Regular exercise．a variety of hobbies，a healthy diet and avoidance of stress．