номер 7, страница 77 - гдз по английскому языку 8 класс (starlight) учебник Баранова, Дули

Four F.

Recreating monsters.

Exercise seven A.

Page seventy-seven.

Back to life.

When the last Pyrenean Ibex died, killed by a falling tree, the species officially became extinct. But scientists had already taken and carefully preserved DNA samples from this wild mountain goat. Using these samples and a domestic goat's ovary eggs, they were able to bring the Pyrenean Ibex back to life. Even though the clone lived for only seven minutes, some scientists claim that advanced techniques could now be used to clone dinosaurs and unleash a real-life Jurassic Park on the world.

Could a T-Rex really walk the Earth again? Well, dinosaurs were roaming the Earth over sixty-five million years ago, and dinosaur DNA doesn't last that long, even in teeth or bones. It is generally accepted that it can survive one hundred thousand years at the most.

Jack Horner, a world-famous paleontologist at Montana State University, however, disagrees.

Of course, we can bring them back to life, he says. The science is there.

In fact, in two thousand and three, Jack and his team made a breakthrough that amazed scientists. While excavating the skeleton of a Tyrannosaurus Rex at a remote site in Montana, its thigh bone broke in two as they were lifting it by helicopter. Back at the university, one of Jack's students was running tests on the bone when she suddenly found organic material. After it was placed under a microscope and magnified four thousand times, she realized she was looking at dinosaur blood vessels, sixty-eight million years old. It was an astonishing finding that suggests that DNA might last a lot longer than originally believed after all.

So does this mean that we will be sharing Earth with cloned T-Rexes in the future? Jack believes it's possible, but a complete genetic map of a dinosaur would have to be worked out first, and that might take decades. For this reason, he is also looking at other ways to revive dinosaurs.

Most scientists believe that birds are distant relatives of certain types of dinosaur and have some dormant DNA from their ancestors. So perhaps the answer lies with birds.

Jack is not the only one following this line of research. At McGill University in Canada, Hans Larson has conducted experiments into reactivating dinosaur DNA in birds. He had been investigating the evolution of dinosaurs' long tails into birds' short tails more than one hundred fifty million years ago. Larson noticed that as an embryo, a chicken's tail has sixteen small bones, but only five when it hatched out of the egg. It seemed that the embryo of a modern-day bird could contain the blueprint for a dinosaur.

Larson found that by changing the genetic makeup of a chicken, he could enlarge its tail by three more bones. This may not seem so impressive, but a series of alterations could result in a completely new kind of dinosaur. Larson is convinced that this reverse evolution means that we could see a type of dinosaur within the next one hundred years.

That seems a long time to wait, but some Japanese scientists are more ambitious. The Tokyo researchers believe that they can bring the woolly mammoth back from the dead very soon. This distant ancestor of an elephant died out eight thousand years ago, so the chances of finding usable DNA are much higher. They intend to go on an expedition to frozen Siberia, where they are optimistic that they will find the necessary organic material.

Scientists like Jack Horner are fascinated by the idea of unlocking the mysteries of a lost prehistoric world. He imagines himself teaching students on stage, accompanied by what he calls a Dino-chicken on a lead. He thinks that would be the most satisfying lecture he could ever give.

Jack says: There is now nothing to stop us bringing back dinosaurs but ourselves. He continues, though, whether it is a good idea or not is another question.