恐龙危机

Anear 20-degree drop in average temperature waskilling the dinosaurs even before a giant asteroidimpact finished them off,according to new researchby a team of Canadian paleontologists(古生物学者).If correct,the finding explains why dinosaurswere so vulnerable to the impact.which many scientistsagree caused the extinction of dinos and other prehistoriccreatures around 65 million years ago.Evidence that climate change led to the dinosaurdemise(死亡)comes from a series of four collections ofdinosaur-era fossils in Alberta(阿尔伯达省),Canada.Thefossils represent the last 10 million years of the Creta-ceous(白垩纪),a relatively short period in geologic time.The Cretaceous spanned 146 to 65 million years ago.Changes revealed by the soil and rock around thefossils.such as the formation of coal and a decrease incertain plant life.indicate a cooldown accompanied by adrop in rainfall.Average temperatures went from a pleasant77 degrees Fahrenheit to a rather chilly 59 degrees.Dinosaurs are thought to have been fairly tolerant oftemperature changes,due to their mammal-like physiolo-gy.But turtles,crocodiles and other large reptiles( 行动物)in their ecosystem(生态系统)would have been more     

The Choice

Four and a half billion years1 ago, the earth was formed. Perhaps a half billion years after that, life arose on the planet. For the next four billion years, life became steadily more complex, more varied, and more ingenious, until, around a million years ago, it produced mankind-the most complex and ingenious species of them all. Only six or seven thousand years ago-a period that is to the history of the earth as less than a minute is to a year-civilization emerged, enabling us to build up a…     

Jeju Island

Jeju Island is a volcanic island,dominated by Halla(汉拿)Mountain:a volcano 1,950 meters high and the highest mountain in South Korea.The island measures approximately 73 kilometers across east to west,and 41 kilometers from north to south.The island was created entirely from volcanic eruptions approximately 2 million years ago,during the time period extending from the Tertiary to the beginning of the Quaternary period,and consists chiefly of basalt and lava.The eruptions took place in the Cenozoic era.     

A new mutation （1062 del 16） of iduronate-2-sulfatase gene from a Chinese patient with Hunter syndrome

Objective: To identify the mutations of iduronate-2-sulfatase (IDS) gene, to reveal its mutation features, and to establish a basis for genetic counseling and prenatal gene diagnosis of Hunter syndrome. Methods: Urine glycosaminoglycans (GAGs) assay, PCR and DNA sequencing were performed to detect mutation of IDS gene of the patient and his parents. Results: The result showed that the patient was: DS( ), HS( ), KS(-), CS(-), and that both of his parents were negative. A frame-shift deletion mutation (1062 del 16) was identified in exon 7 of the patient's IDS gene. His parents' genotypes were normal. Conclusion:The patient's mutation was not inherited by his parents but a novel one. The mutation probably altered the primary structure and tertiary structure of IDS enzyme protein remarkably and lowered the activity of IDS enzyme greatly. Therefore it is supposed to be the direct cause of the disorder.     

Why the Rabbit＇s Tail Is Short

Thousands of years ago, none of the animals of the forest had a tail. Lion was the king of the forest. One day, the lion ordered (命令) all the animals to go to the old pagoda tree (槐树) to get a tail. During the day time, if somebodydidn' t arrive, it could not get a tail, and would be driven out of the forest.     

高中生活(英文)

A:Jacky.remember your first day of freshmanyear(一年级)in high school? B:My first day of freshman in h high school islike 1 million years ago. Your question opens thedoor to the past. A:Lots of memories of those good old days.huh?     

How Old Is the Universe?

For years, astronomers struggled to calculate the age of the universe. Estimates ranged from 10 to 20 billion years old, a frustratingly large spread. But that was before the launch of the Hubble Space Telescope, named after the astronomer whose discovery 70 years ago began the quest to learn the universe's age.     

狗能教人新把戏?(英文)

The adage(谚语) that you cannot teach an old dog new tricks may be the wrongway round. It could have been that new tricks were taught to people by dogs more than 100, 000 years ago,prompting(促进,激励) humankind to take a leap(跳跃,飞跃) in development leading to modern culture and society, Australia-based researchers said this week.     

阅读理解两则(英文)

(A) More than seven hundred years ago,the Prince of Wales had a very big and brave dog called Gelert. One day the Prince wanted to go hunting with his men.He told his dog to stay at home and look after his baby son.The baby was in a wooden cradle(摇篮),which was like a small bed. When the Prince came back from hunting,Gelert ran out to meet his     

President Bush Calls on Senate to Back Human Cloning Ban布什总统呼吁参议院支持人类克隆禁令（节选）

We live in a time of tremendous medical progress. A little more than a year ago, scientists first cracked(解读)the human genetic code(基因密码)-one of the most important advances in scientific history, Already, scientists are developing new diagnostic (诊断的) tools so that each of us can know our risks of disease and act to prevent them.     

Development of a pyrF-based counterselectable system for targeted gene deletion in Streptomyces rimosus

Streptomyces produces many valuable and important biomolecules with clinical and pharmaceutical applications. The development of simple and highly efficient gene editing tools for genetic modification of Streptomyces is highly desirable. In this study, we developed a screening system for targeted gene knockout using a uracil auxotrophic host(Δpyr F) resistant to the highly toxic uracil analog of 5-fluoroorotic acid(5-FOA) converted by Pyr F, and a non-replicative vector p KC1132-pyr F carrying the complemented pyr F gene coding for orotidine-5'-phosphate decarboxylase. The pyr F gene acts as a positive selection and counterselection marker for recombinants during genetic modifications. Single-crossover homologous integration mutants were selected on minimal medium without uracil by reintroducing pyr F along with p KC1132-pyr F into the genome of the mutant Δpyr F at the targeted locus. Double-crossover recombinants were generated, from which the pyr F gene, plasmid backbone, and targeted gene were excised through homologous recombination exchange. These recombinants were rapidly screened by the counterselection agent, 5-FOA. We demonstrated the feasibility and advantage of using this pyr F-based screening system through deleting the otc R gene, which encodes the cluster-situated regulator that directly activates oxytetracycline biosynthesis in Streptomyces rimosus M4018. This system provides a new genetic tool for investigating the genetic characteristics of Streptomyces species.     

哭出来就好了

I remembered losing my father to a sudden car accident a number of years ago.I tried to remain strong through it all.One day,when a song came on the radio that reminded me of my dad,I completely 1)lost it.It was the first time since the 2)funeral that I just 3)let go and cried.It felt good to not 4)hold back anymore.     

An Honest Boy

Jim is an honest(诚实的) boy. He is fifteen years old. His parents died three years ago and he had to make a living by himself. One day, when he was walking in the street, he found a wallet(钱包) full of money. He found     

Deletions in the genomes of fifteen inbred mouse lines and their possible implications for fat accumulation

Copy number variants (CNVs) are pieces of genomic DNA of 1000 base pairs or longer which occur in a given genome at a different frequency than in a reference genome. Their importance as a source for phenotypic variability has been recognized only in the last couple of years. Chromosomal deletions can be seen as a special case of CNVs where stretches of DNA are missing in certain lines when compared to the reference genome of the mouse line C57BL/6, for example. Based upon more than 8 million single nucleotide polymorphisms (SNPs) in the fifteen inbred mouse lines which were determined in a whole genome chip based resequencing project by Perlegen Sciences, we detected 20166 such long chromosomal deletions. They cover altogether between 4.4 million and 8.8 million base pairs, depending on the mouse line. Thus, their extent is comparable to that of SNPs. The chromosomal deletions were found by searching for clusters of missing values in the genotyping data by applying bioinformatics and biostatistical methods. In contrast to isolated missing values, clusters are likely the consequence of missing DNA probe rather than of a failed hybridization or deficient oligos. We analyzed these deletion sites in various ways. Twenty-two percent of these deletion sites overlap with exons; they could therefore affect a gene's functioning. The corresponding genes seem to exist in alternative forms, a phenomenon that reminds of the alternative forms of mRNA generated during gene splicing. We furthermore detected statistically significant association between hundreds of deletion sites and fat weight at the age of eight weeks.     

Stories About Dogs

Dogs are flesh-eating animals. From the Stone Age( 石器时代) menlived in caves( 洞穴). The dogs first became man?s friends. Soon the mentrained( 训练) the dogs to help people in the hunt to carry their burdens(担子), to guard their camps and so on.Dogs have a fine sense of smell ( 嗅觉). They can go in search ofmissing things. For example, a golden seal(图章) in a museum(博物馆)was missing some years ago, and the policemen searched for it every-where in vain(徒劳). Finally a dog found the go…     

Is It Worth the Risk?

<正>A number of years ago (1983- 1987), I had the opportunity to play the character of Ronald McDonald for the McDonald’s Corporation.One of our standard events was"Ronald Day."One day each month, we     

The Role of the Woman in the Language Development of the Child

The studies in language acquisition can be traced back to over a hundred years ago.Because of the interest they had in child development at that time,many researchers went into studies on child language or language acquisition.This paper has examined child language and language acquisition in detail,tracing the history from the earliest studies on the subject to fairly present day.The paper will also look at variations among children at early cognitive development.The role of the woman with particular reference to the 21st century will be discussed.The guiding principles will be the linguistic environment and the cultural influence on the child.     

画笔下的莫斯塔尔

I started doing 1)watercolor travel 2)sketches three years ago,in order to move at a slower pace and create richer memories of the places I visited.And so I arrived in Mostar,a small city in southern Bosnia and Herzegovina.     

勇敢的上海女人(英文)

As the city emerges as China's commercial hub(中心), it is also becoming-more than ever-a mecca(众人都渴望去的地方) for women's opportunity.As Jane Zhang grew up in Shanghai 25 years ago, her family ate dumpings (面团) made of corn husks (壳) and lived in one room. Several years ago, she opened China's first temp(临时雇员) agency, quitting a secure job as a mechanical-drawing teacher against the advice of her friends.Diminutive(体型小巧的) and peppery(泼辣的), Zhang says her women employees show flexibility (适应性) and focus "in the new business world of Shanghai".     

Shenandoah

Hundreds of years ago an Indian chief named Shenandoah lived in what is now the state of Virginia. Little is known about Shenandoah, but the soft sound of the name was given to a river.