VOA Special English 慢速英语听力材料

SCIENCE IN THE NEWS - March 5, 2002: Digest

VOICE ONE:

This is Sarah Long.

VOICE TWO:

And this is Bob Doughty with Science in the News, a VOA Special English program about recent developments in science. Today, we tell about the first genetic copy of a cat. We tell about scientists who are playing love songs for sharks. And we tell about the deaths of hundreds of millions of butterflies in Mexico.

((THEME))

VOICE ONE:

American scientists in the state of Texas have produced a genetic copy of a cat for the first time. This cloned baby cat was born in December. Its birth marks the first successful cloning of an animal commonly kept as a pet. During the past few years, other researchers have cloned sheep, mice, pigs, cows and goats.

The scientific journal Nature reported the cloning of the cat last month. The kitten is called "c-c" for "copy cat" or "carbon copy." C-c was created at the College of Veterinary Medicine of Texas A-and-M University. This school for doctors who treat animals is in College Station, Texas. Mark Westhusin (west-TOO-shin) led the team that created the kitten.

VOICE TWO:

Scientists usually clone animals by placing a cell from an adult animal into a special egg cell whose genetic material has been removed. The genes in the adult cell direct the development of the embryo. The process means that the newly born creature will be an exact genetic copy of the adult.

Doctor Westhusin and his team first tried to create a male kitten. They took cells from a male cat's mouth and joined them with the specially treated egg cells. This produced more than eighty cloned embryos. The researchers then placed the embryos in seven female cats. One of these cats became pregnant. However, the pregnancy ended too soon.

Doctor Westhusin and the other researchers tried again. They took cells from the ovaries of a female cat named Rainbow and joined them with the special egg cells. They placed five cloned embryos into a female cat called Allie. Allie became pregnant. Sixty-six days later, the doctors assisted in the birth of a normal, healthy kitten.

VOICE ONE:

C-c is now more than two months old. She has continued to develop normally. She has exactly the same genes as Rainbow. But she does not look exactly like her. The cats have different colored markings. This is because their colors are decided partly by genes and partly by molecular changes during development.

Doctor Westhusin's team has been trying to develop a cloned dog for several years. However, they say cloning a dog is much more difficult. They say scientists know more about cats because they have worked much more with cat eggs and embryos. Cats produce eggs when they mate. Dogs, however, do not produce eggs at any special time.

Doctor Westhusin says research on cloning cats and dogs has provided important information about their reproduction. He says this information could help develop new methods of preventing the birth of unwanted animals. He also says cloning could be used to produce identical animals in research to find cures for diseases in humans. Researchers also say information from cloning could help save large endangered cats, like the African wild cat.

VOICE TWO:

A company called Genetic Savings and Clone of College Station, Texas, supported the research. The company wants to offer cloning to owners of cats and dogs in the future. The company believes some people may want to clone their pets when the animals die.

However, many groups that are concerned with the treatment of animals oppose cloning cats and dogs. They say it serves no useful social purpose. And they say it would add to the problem of too many pets in the United States. Each year, American animal shelters destroy millions of unwanted dogs and cats.Some people also fear that the cloning of a cat means another step toward cloning humans. Some scientists already say they are working toward that goal.

((MUSIC BRIDGE))

VOICE ONE:

Scientists at the National Sealife Center in Birmingham, England have a problem with their sharks. They want the five male and five female sharks to mate. Yet none of the creatures has shown any interest in the opposite sex. The center has had success in getting other sea creatures to reproduce. Some of those creatures live in the same area with the sharks.

The British scientists seem willing to try almost anything to get the sharks to mate. Recently, they started to play love songs near a large container of water where the sharks live. The scientists hoped that the music would get the creatures ready for mating.

VOICE TWO:

The scientists decided to play music after they heard about a study done by the Rowland Institute for Science in Cambridge, Massachusetts. In the American study, scientists tested different sounds on koi carp fish. These scientists found that the fish react to sounds in a way similar to humans. They showed that the koi are affected by and can identify different kinds of music.

Sharks have excellent hearing. But it is limited to low-pitched sounds. The scientists in Birmingham started playing music for the sharks just a few days before February fourteenth. That was Saint Valentine's Day, the yearly celebration for lovers. They played a number of popular love songs, including some by American singer Barry White.

((MUSIC INSERT: "YOU'RE THE FIRST, THE LAST, MY EVERYTHING"))

VOICE ONE:

Scientists played the music in the room where the sharks live. The scientists say they may consider an idea to play the music underwater.

The researchers say they are not sure how long it would be before the music has an effect. How will the scientists know if their experiment is successful? They say that, before mating, the male shark will chase the female and attempt to bite her on the back.

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VOICE TWO:

Scientists say the loss of hundreds of millions of monarch butterflies in central Mexico is not expected to threaten the species. The butterflies froze to death in January after a severe winter storm. Most of the butterflies in the Rosario and Sierra Chincua colonies were killed in the storm. The colonies are in the mountains in the state of Michoacan, west of Mexico City.

Researchers say the butterflies froze to death after heavy rain fell in the area, followed by freezing temperatures. Scientists say the temperatures following the storm were the lowest recorded in the area in the past twenty-five years.

VOICE ONE:

During the year, monarch butterflies fly long distances, or migrate. They are one of the few kinds of insects that migrate. This has made the monarch popular among nature lovers.

The monarchs spend the winter in Mexico. Each spring, the butterflies fly north after they mate. The females stop to lay their eggs in the southern United States. The adults die soon after. The monarchs that develop from those eggs continue the flight. They return to the same areas in North America where their parents lived. By summer, the butterflies can reach as far north as Canada.

During the autumn, the monarchs return to the same forests in the mountains of Mexico. They like the oyamel tree the best. These tall trees are sometimes completely covered with butterflies.

VOICE TWO:

Some scientists have suggested that the loss of forests in the mountains of Mexico led to the die-off of monarchs. They say the remaining forests may no longer provide enough protection to keep the butterflies warm and dry. Every winter, millions of monarchs die in the high mountain forests.

However, scientists note that the species is not in danger of disappearing. That is because there are other, smaller populations of monarchs in the United States that did not migrate to Mexico. Scientists say they will know after more study if the monarch populations in Mexico will be able to recover from the die-off.

((THEME))

VOICE ONE:

This SCIENCE IN THE NEWS program was written by Jerilyn Watson, George Grow and Cynthia Kirk. It was produced by Cynthia Kirk. This is Sarah Long.

VOICE TWO:

And this is Bob Doughty. Join us again next week for more news about science in Special English on the Voice of America.