1 What Are Transgenic Plants and Animals? Transgenic plants and animals result from genetic engineering experiments in which genetic material is moved from one organism to another, so that the latter will exhibit a characteristic. Business corporations, scientists, and farmers hope that transgenic techniques will allow more cost-effective and preci plants and animals with desirable characteristics that are not available using up to date breeding technology. Transgenic techniques allow genetic material to be transferred between completely unrelated organisms. In order for a transgenic technique to work, the genetic engineer must first construct a transgene, which is the gene to be introduced plus a control quence. When making a transgene, scientists usually substitute the original promoter quence with one that will be active in the correct tissues of the recipient plant or animal. The creation of transgenic animals is one of the most dramatic advances derived from recombinant DNA technology. A transgenic animal results from inrtion of a foreign gene into an embryo. The foreign gene becomes a permanent part of the host animals’ genetic material. As the embryo develops, the foreign gene may be prent in many cells of the body, including the germ cells of the testis or the ovary. If the transgenic animal is fertile, the inrted foreign gene (transgene) will be inherited by future progeny. Thus, a transgenic animal, once created, can persist into future generations. Transgenic animals are different from animals in which foreign cells or foreign organs have been engrafted. The progeny of engrafted animals do not inherit the experimental change. The progeny of transgenic animals do. The techniques for creating a transgenic animal include the following: 1) picking a foreign gene, 2) placing the foreign gene in a suitable form called a “construct” which guides the inrtion of the foreign gene into the animal genome and encourages its expression, and 3) injecting the construct into a single fertilized egg or at the very early embryo stage of the host animal. Much genetic engineering goes into the choice of a foreign gene and building a construct. The construct must have promotes to turn on foreign gene expression at its new site within the host animal genome. By choosing a particular promoter and splicing it in front of the foreign gene, we can encourage expression of our transgene within a specific tissue. One of the most important applications of transgenic animals is the development of new animal models of human dia. Transgenic animals can rve as models for many malignant tumors. Although mice have been the most frequent hosts for transgenic modification, other domestic animals have also been ud. One idea has been to create transgenic cows which crete important pharmaceutical substances in their milk. “Other attempts are being made to express human interferon in the milk of sheep”. A transgenic crop plant contains a gene or genes which have been artificially inrted instead of the plant acquiring them through pollination. The inrted gene quence (known as the transgene) may come from another unrelated plant, or from a completely different species: transgenic Bt corn, for example, which produces its own incticide, contains a gene from a bacterium. Plants containing transgenes are often called genetically modified or GM crops although in reality all crops have been genetically modified from their original wild state by domestication, lection and controlled breeding over long periods of time. A plant breeder tries to asmble a combination of genes in a crop plant which will make it as uful and productive as possible. Depending on where and for what purpo the plant is grown, desirable genes may provide features such as higher yield or improved quality, pest or dia resistance, or tolerance to heat, cold and drought. Combining the best genes in one plant is a long and difficult process, especially as traditional plant has been limited to artificially crossing plants within the same species or with cloly related species to bring different genes together. For example, a gene for protein in soybean could not be transferred to a completely different crop such as corn using traditional techniques. Transgenic technology enables plant breeders to bring together in one plant uful genes from a wide range of living sources, not just from within the crop species or from cloly related plants. 摩羯座的守护星 This technology provides the means for identifying and isolating genes controlling specific characteristics in one kind of organism, and for moving copies of tho genes into another quite different organism, which will then also have tho characteristics. This powerful tool enables plant breeders to do what they have always done ― generate more uful and productive crop varieties containing new combinations of genes ― but it expands the possibilities beyond the limitations impod by traditional cross-pollination and lection techniques. Overall, the u of transgenic technology has many advantages over traditional methods. Transgenic breeding is said to be more specific, faster, and less costly. Right now rearch is limited traits involving one or a few genes. Before scientists can manipulate complex traits, there is going to be the need for many years of rearch. | |
2 How Richard Branson Works Magic Richard Branson, chairman of the Virgin Group, has parlayed a lifelong disdain for conventional business wisdom into a $3.5 billion international conglomerate and one of the world’s most powerful and recognizable brands. Under the ubiquitous Virgin banner, Mr. Branson has ventured into a panoply of business ― from condoms to wedding gowns, from airlines to financial rvices ― and in the process has taken on entrenched giants and wrested market share from them. All the while, the flamboyant and irreverent Mr. Branson has tweaked the business establishment, particularly in Britain, and displayed a good command of publicity and showmanship to gain priceless cachet for the Virgin brand. He has been, for much of the past 30 years, one of the most admired Britons, and his fame has spread in recent years around the globe as Virgin has expanded its reach and its luster. Mr. Branson loves nothing more than a daunting challenge; he views the impossible as just another business opportunity. His trademark is outlandish publicity stunts. He will do almost anything to promote the Virgin brand: driving a tank down Fifth Avenue in New York to introduce Virgin Cola to the United States, risking his life in high-profile hot-air balloon adventures or portraying a drowning victim on television’s “Baywatch.” But Mr. Branson stands for more than balloon trips and powerboat races across the Atlantic. Behind the brash and insouciant huckster, there lies a sharp business visionary who has created a formula for success that is rife with lessons for chief executives in any country and any business. Mr. Branson’s success reflects an uncanny ability to take the consumer’s point of view as his own and find ways to embrace that view for profit. Despite his personal riches, Mr. Branson has retained an “everyman” persona marked by his casual dress, affable and modest manner, and devilish disrespect for convention. He understands viscerally the concerns and needs of his customers and his employees and acts as a conduit for fulfilling tho needs. He has built the Virgin brand in his own image, and the result is an extremely positive emotional bond between consumers and companies that bear the Virgin label. It is brand-builder’s nirvana, made all the more impressive becau the brand is all that ties together more than a hundred disparate Virgin business. There is little synergy or shared resources among the Virgin companies; Virgin, in fact, rembles the classic Japane keiretsu such as a Yamaha or Mitsubishi. | |
3 Spaceships of the Future The furthest we have been is the Moon. If we want to travel into deep space, beyond our own backyard, the Solar System, we’ll need a new breed of spacecraft It may be the oldest cliché in town, but in the not too distant future science fiction will turn into science fact. The fantastic spaceships of sci-fi comic books and novels will no longer be a figment of our creative imagination; they may be the real vision of our future. 男人想娶你的四个信号 Engineers and designers are already designing craft capable of propelling us beyond Earth’s orbit, the Moon and the planets. They’re designing interstellar spaceships capable of travel across the vast emptiness of deep space to distant stars and new planets in our unending quest to conquer and discover. Our Univer contains over a billion galaxies; star cities each with a hundred billion inhabitants. Around the stars must exist planets and perhaps life. The temptation to explore the new realms is too great. First things first ― we’ll have to build either a giant orbiting launch platform, far bigger than the International Space Station (ISS), or a permanently manned lunar ba to provide a springboard for the stars. Some planners feel we should limit ourlves to robotic probes, but others are firmly committed to nding humans. “There’s a debate right now about how to explore space” says astronaut Bill Shepherd, destined to be the first live-aboard Commander of the ISS. “Humans or machines ― I think they’re complementary”. The human problem Space is the most hostile environment we will ever explore. Even a single five-hour spacewalk requires months of training, and a vast technical backup to keep it safe. The astronauts and cosmonauts who live aboard the ISS will be there for only a few weeks or months; if we want to travel into deep space it could take years. First we’ll have to find out just how long the human body can survive in a weightless environment. In zero gravity, four pints of body fluid rush from the legs to the head where it stays for the duration of the mission. Astronauts often feel as if they have a permanent cold, and disorientation can become a major problem. In space there’s no physical nsation to let you know when you’re upside down and astronauts have to rely on visual clues from their surroundings. A few hours after reaching orbit, one in three of all astronauts will experience space sickness ― a feeling rather like carsickness. And weightless conditions lead to calcium being leached from the bones, and problems with the astronauts’ immune systems. Trillions of rocky fragments ― meteoroids ― roam our Solar System at speeds of up to 150,000 miles an hour. A meteoroid no bigger than a grain of salt could pierce a spaceship window. Protection from the extreme hazards of space is going to need some clever technology. Space is also full of lethal radiation ― X-rays, gamma rays and the high-speed particles called cosmic rays. Down here on Earth we are protected by the atmosphere and by our planet’s magnetic field, but in space long haul astronauts suffer gradual but irreversible radiation sickness unless they are carefully shielded. Commander Shepherd is confident the ISS will help us crack the problems “The ISS is going to answer a number of questions about long range exploration in space. A lot of things are going to be pioneered on the space station for future exploration”. Stepping stones Saturn V is still the most powerful rocket ever built. But even this vast 3000 tonne giant carried only enough fuel to nd a tiny manned capsule with just three men on a 250,000 mile journey ― a mere drop in the cosmic ocean. It’s over a quarter of a century since the last man stood on the Moon (Commander Gene Cernan on the Apollo 17 mission in 1972), and it ems that it will be another quarter of a century before we return to build a permanently manned ba there. Bob Forward ― who earns his living from designing spaceships of the future ― believes we’ll have to find a cheap way of reaching the Moon before we think of living there. His slingshot concept may em radical at the start of the 21st century, but it is certainly ingenious. “If you have something rotating quite fast around another thing on the end of a string, it has a tendency to fly away. You have to decide when to let go (from Earth-orbit) and ― like a trapeze artist catching his partner ― you have to decide when to catch the payload (in lunar orbit)”. A lunar ba would become a viable stepping stone to deep space. In the 1990s, the Clementine and Lunar Prospector spacecraft detected frozen water below the lunar surface. This could be mined, melted and broken down to make liquid oxygen and hydrogen rocket fuel needed to blast off into deep space. But before we leave the Solar System on our interstellar quest we will have to conquer it. Mars will become our first target. Whether we’ll reach it directly from Earth, from Earth’s orbit or from the Moon is anyone’s guess but Mars is far from being a barren dert like the Moon. Mars probably has plentiful supplies of frozen water below the surface and even has 24-hour days! Unfortunately the atmosphere is 95% carbon dioxide, with just a fraction of the Earth’s atmospheric pressure and no protective ultraviolet layer. Martian astronauts will have to live in aled modules, and wear spacesuits to venture outside. Mars would be a tiny colony, like the remote outposts of the early Earth explorers. Mars itlf will probably never be a stepping stone to the stars, but it will help us learn if we can live in such a remote and harsh place for years or even a lifetime. It’s only rocket science Scientists are already experimenting with propulsion systems that may travel much faster than today’s conventional chemical rockets. Franklin Chang’s plasma rocket may be the answer. “In a plasma rocket you’re continually accelerating,” he explains. A trip to Mars could be cut to 90 days, claims Chang. His rocket harness a nuclear process to produce a hot gas plasma. The plasma is magnetically held in a rocket the shape of a bottle and then expelled at very high velocity to provide propulsion. The plasma has to be heated to millions of degrees. Chang believes his system will be too good just to reach Mars. “I think it will quickly be developed for interplanetary travel within our Solar System”. The plasma rocket is now under development at NASA’s Houston laboratories. Another new method of propulsion is already flying through our Solar System. Pushed only by an electronically driven ‘ion engine’, Deep Space One is already over 100 million miles from Earth. It works by ionising xenon gas and expelling it with the aid of electric fields, so providing a gentle but constant thrust. The ion engine provides a force about the same as a single sheet of paper exerts on your hand ― far too weak to lift a spacecraft from the surface of a planet ― but the continuous acceleration has already pushed Deep Space One to a speed ten times higher than any of the manned rockets we u today. Interstellar travel To leave the Solar System and carry humans to the stars we will have to find a way of travelling near to the speed of light. Even then a journey could take hundreds or thousands of years. Travelling at 1/10 the speed of light it would take over forty years to reach the nearest star, Alpha Centauri. One giant source of free energy is our Sun. Bob Forward has designed the solar sail, a craft that doesn’t have to carry its own fuel supply. It’s driven by the power of the Sun’s rays, and it will be the fastest machine ever built. “The sunlight bounces off the aluminium sails and in the process gives it a tiny push,” explains Forward. Like the ion probe it will accelerate and accelerate. And it’s not a total dream. NASA is already experimenting with deploying large sails in Earth-orbit. Propelled by light, solar sails will travel thousands of times faster than Apollo or the Shuttle. Asleep or awake? Even with the perfect spaceship it isn’t going to be easy. In his classic sci-fi novel 2001, Arthur C. Clarke ud the concept of suspended animation as a way for humans to cope with long space flights. He imagined that we would be able to put the human body into hibernation ― suspended animation ― to escape the boredom of long interstellar missions. An even more drastic measure might be to freeze the astronauts. We already u cryogenic techniques to prerve dead bodies and store human embryos. Freezing living adults may not be so far away, but perhaps we won’t have to do that. Perhaps we should u our existing technology and nd frozen embryos across to the far corners of the cosmos. It could certainly save on space. Then hundreds of years from now, billions and billions of miles away, the embryos will be thawed and their hearts will start beating. The space-farers of the future will not grow inside a mother’s body but will be incubated in a machine. They will be brought up by robot. It may em strange and radical but one day it might just happen… | |
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