Science

ScienceCan people change their skin colour without suffering like pop king Michael Jackson? Perhaps yes. Scientists have found the gene that determines skin colour.The gene comes in two versions, one of which is found in 99 per cent of Europeans. The other is found in 93 to 100 per cent of Africans, researchers at Pennsylvania State University report in the latest issue of Science.Scientists have changed the colour of a dark-striped zebrafish to uniform gold by inserting a version of the pigment(色素) gene into a young fish. As with humans, zebrafish skin colour is determined by pigment cells, which contain melanosomes(黑色素). The number, size and darkness of melanosomes per pigment cell determines skin colour.It appears that, like the golden zebrafish, light-skinned Europeans also have a mutation(变异) in the gene for melanosome production. This results in less pigmented skin.However, Keith Cheng, leader of the research team, points out that the mutation is different in human and zebrafish genes.Humans acquired dark skin in Africa about 1.5 million years ago to protect bodies from ultra-violet rays of the sun(太阳光紫外线), which can cause skin cancer.But when modern humans leave Africa to live in northern latitudes, they need more sunlight on their skin to produce vitamin D. So the related gene changes, according to Cheng.Asians have the same version of the gene as Africans, so they probably acquired their light skin through the action of some other gene that affects skin colour, said Cheng.The new discovery could lead to medical treatments for skin cancer. It also could lead to research into ways to change skin colour without damaging it like chemical treatment did on Michael Jackson.51. The passage mainly tells us that ________.A. people can not change their skin colour without any painB. the new discovery could lead to search into ways to change skin colour safelyC. pop king Michael Jackson often changed his skin colour as he likedD. scientists have found out that people’s skin colour is determined by the gene52. It can be inferred from the passage that ________.A. nowadays people who want to change their skin colour have to suffer a lot from the damagecaused by the chemical treatmentB. Europeans and Africans have the same geneC. the new discovery could help to find medical treatments for skin cancerD. there are two kinds of genes53. Scientists have done an experiment on a dark-striped zebra fish in order to ________.A. find the different genes of humans’B. prove the human s’ skin colour is determined by the pigment geneC. find out the reason why the African s’ skin colour is darkD. find out the ways of changing peopl’s skin colour54. The reason why Europeans are light-skinned is probably that ________.A. they are born light-skinned peopleB. light-skinned Europeans have mutation in the gen for melanosome productionC. they have fewer activities outsideD. they pay much attention to protecting their skin55. The writer’s attitude towards the discovery is ________.A. neutralB. negativeC. positiveD. indifferentIt’s food scarcity (短缺), not dietary preferences, that motivates birds to migrate thousands of miles back and forth between breeding and non-breeding areas each year, new research shows. “It’s not whether you eat insects, fruit, nectar or candy bars or where you eat them — it matters how reliable that food source is,” said study leader W. Alice Boyle of the University of Arizona. To figure out the pressures that drive some birds to leave home for the season, Boyle examined 379 related species of flycatchers and compared their sizes, food types, habitats, migratory behaviors and whether or not they fed in flocks.To compare the birds, the researchers constructed a “supertree” showing the exact evolutionary（演化的）relationships among different species.A computer analysis then determined whether a particular species was migratory because it ran in the “family” or whether something in the bird’s environment was forcing it to leave each season.Boyle and her colleagues found that food scarcity was the number one issue that predicted a species’ migratory behavior.An alternative strategy that birds use to deal with food scarcity is to forage (四处搜寻) in flocks, because a group is more likely to find a new source of food than a lone individual.“If you are faced with food scarcity, you have two options,” Boyle said. “You can either forage with other birds, or you can migrate.”51. The passage mainly tells us ________.A. the real reason for birds’ migrationB. food scarcity that birds face todayC. how birds search for foodD. when birds migrate52. The scientists used to believe that birds migrate because ________.A. they want to search for the food they likeB. they can find more food in a different placeC. they can breed their young in a different placeD. the weather turns too cold53. The researchers constructed a “supertree” mainly to ________.A. compare the sizes of different birdsB. make out the relationships between different birdsC. find out what causes birds to leave each seasonD. predict when the birds were migratory54. Which of the following is true?A. All birds fly to non-breeding areas each year.B. There are 379 species of birds migrating.C. Two related species have the same behavior.D. Computers are used in the research work.55. The passage suggests that ________.A. different kinds of birds have different ways to migrateB. different kinds of birds migrate for various reasonsC. some birds can survive without migrating each seasonD. birds’ food sources are becoming rare all over the worldAn Australian-based scientist announced yesterday he had made a step forward in forensic (用于法庭的) DNA testing so that an individual can be identified by asingle cell.Ian Findlay, from the Australian Genome Research Facility at the University of Queensland, said current DNA testing required 200 to 500 cells to gain a similar level of accuracy. "What we have done has brought that down to one cell," Dr Findlay said after releasing details of his DNA testing technique at a Sydney conference.The technology could allow investigators to pick up DNA identities from plastic cards and even build up a complete history of the people who have handled a paper document."You'd have to wear a space suit to stop yourself from leaving traces. You can identify cells on the paper, so you can work out where it's come from and who's touched it,” he said.The technique could also be used to trace the thrower of a punch（打孔）from cells left behind on the skin of their victim. Even the wearing of latex（橡胶）gloves would not help: small cells can pass through the gloves, and the constant flow of genetic material given off by the human body would leave further evidence."We gained a skin cell from a document dating back 30 years and managed to gain a DNA fingerprint. DNA evidence can remain fresh for decades, perhaps even centuries," Dr Findlay said. "The potential for this technology to solve unsolved crimes is great, "he said.But Dr Findlay, named scientist of the year in 1998 by the European Society of Human Genetics, said the new testing needed to be scientifically validated, which would take up to five years.He said, "There are serious consequences taking on technologies too early. The public has to be sure that they have the utmost confidence in the security and court systems."51. The main advantage of the new technology is that ______.A．a single cell can identify an individualB．it has brought down the cost of DNA testingC．a higher level of accuracy can be acquired with a single cellD．it needs less than 200 cells to gain a certain level of accuracy52. The underlined word" validated" means ______.A. confirmedB. imaginedC. supposedD. criticized53. According to Ian Findlay, the new technology can ______.A. help to keep DNA evidence fresh for decades and even centuriesB. make the process of DNA testing much more simplifiedC. help to pick up DNA identities more easilyD. be widely used in five years at most54. The last paragraph suggests that ______.A. the immediate adopting of the technology may cause mistakesB. the public have acknowledged the new testing technologyC. it is safe to put the new technology into use nowD. Dr Findlay is quite sure of his new technology55. The aim of the passage is to ______.A. praise Ian Findlay for his workB. report a piece of interesting newsC. inform us of the wide use of DNA testingD. tell us a recent improvement in DNA testingA single night of taking the drug Ecstasy(摇头丸) can cause serious brain damage and speed up the start of Parkinson's disease, scientists say. Just two to three Ecstasy tablets -- a quantity thatthousands of clubbers take during parties -- can permanently destroy brain cells that affect movement and reasoning, according to American research that links the drug to Parkinson's for the first time.A study by a team at Johns Hopkins University in Baltimore, Maryland, involving squirrel monkeys and baboons(狒狒) found that both species suffered permanent damage to key cells called dopamine neurons, which are lost in Parkinson's, after receiving three low doses of Ecstasy at three-hour periods.The study is particularly significant because baboons are one of the best animal models for the human brain. George Ricaurte, who led the research, said that widespread abuse of the drug may already be claiming victims of such neurological(神经性的) damage. “The most troubling result is that young adults using Ecstasy may be increasing their risk for developing Parkinsonism as they get older.”Alan Leshner, a former director of the US National Institute on Drug Abuse, said: “This study emphasizes the multi-aspect damage that Ecstasy can do to users. We've long known that repeated use damages brain cells. This study shows that even very occasional use can have long-lasting effects on many different brain systems. It sends an important message to young people: don't experiment with your own brain.”Janet Betts, the Essex mother whose daughter Leah died after a single Ecstasy tablet in 1995, said: “This comes as no surprise. People can't see the effects at first, and they’re in permanent denial(否认), saying it's not going to happen to them. But we'll see the symptoms later, just as we have with smoking.”51. The article is intended to .A. explain the effects of the drug Ecstasy on many different brain systemsB. warn youngsters of the risk of taking the drug EcstasyC. convince people of the abuse of the drug EcstasyD. tell us the links between the drug Ecstasy and Parkinson's disease52. According to the passage, Parkinson’s is .A. the name of a scientistB. a kind of brain cellC. be name of an animalD. a kind of disease53. We know from the passage that low doses of Ecstasy .A. won’t cause serious brain damageB. can permanently destroy one’s brain cellsC. can’t show any effect in an experimentD. may bring on Parkinson’s at once54. Why are squirrel monkeys and baboons involved in the experiments?A. Because their brain is similar to human being’sB. Because these animals usually take drugs.C. Because these animals will soon get well after the experiment.D. Because there is a model in the animals’ brains.55. The underlined word "This" in the last paragraph means “”.A. Leah died after a single Ecstasy tablet in 1995.B. people have long known that repeated use of the drug damages brain cellsC. occasional use of the drug can have long-lasting effects on one’s brain systemsD. taking drug has the same symptoms as smokingIn the story of the three little pigs, the one who built his house of straw did not do well; the big bad wolf blew it down. But builder Michael Furbish, who made his own home from bales (捆) of straw, and an elementary school from the same material, says that in reality straw houses are not only strong, but also good for the environment. Straw—the stalks (杆，茎) of plants like wheat, oats, and barley—is considered a waste material and is commonly used on farms as animal bedding. But more and more people are discovering that straw baled into rectangular blocks is an excellent and inexpensive building material.There are two ways to make a straw-bale structure. You can build load-bearing walls with them, which means the walls support the roof. Or you can build a post-and-beam wooden frame that supports the roof and fill in the walls with the bales. Either way, the walls are there to stay. And they provide great insulation(绝缘), helping keep straw houses in cold climates warm in winter and those built in hot places like the desert cool in summer. Straw is considered a "green" building material because it is a renewable resource: a whole new crop can be grown and harvested every year, easily "renewing" the supply. Also, planting and harvesting straw uses relatively little energy. "Most other building materials require a lot of energy to be produced," explains Furbish. "With straw-bale construction, you are getting a building product without using much energy at all."Furbish used about 900 straw bales in his family's two-story, three-bedroom house. His company also provided straw-bale walls for the Friends Community School of College Park in Maryland. That project used about 4,000 bales. When asked if there are any problems with living in a straw house, like mice nibbling (咬，啃) on the walls, Furbish points out that the straw is completely covered with plaster and stucco (灰泥). Besides, he has a couple of cats on mouse watch, just in case. "It would be hard to find a wall system that will wear better than straw," he says. The big bad wolf is just out of luck.51. The author wrote the passage in order to ________.A. prove that the tale of the three pigs and the wolf is wrongB. teach readers how to build straw housesC. introduce an environmentally-friendly building materialD. advertise Furbish’s special houses52. What do we learn about straw houses from the passage?A. It costs little to make such special houses.B. The outsides of the houses are green.C. They are mostly built in the desert.D. Plaster and stucco help make the houses strong.53. The writer mentions the wolf at the beginning and the end of this passage to suggest ________.A. straw houses are in fact nice and strongB. the big bad wolf can never blow the straw houses downC. the big bad wolf is very unluckyD. people in straw houses needn’t worry about wolves54. According to the passage, which of the following statements is TRUE?A. Straw is a waste of material as animal bedding.B. Furbish built his home and an elementary school with only bales of straw.C. Building straw houses requires no energy at all.D. The roof of a straw house can be supported by a wooden frame.55. We can infer from the passage that ________.A. living in a straw house, one has to keep several catsB. the walls of a straw house help keep heat inside in cold climatesC. it is best to build a straw house at harvest timeD. we need 900 straw bales to build one straw house。