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1、四箭齊發(fā)公眾微信四箭齊發(fā)公眾微信KL S T F J PAGE PAGE 6TheIdentificationoftheGeneticParagraph1：Thehistoryofbiologyisfilledwithincidentsinwhichresearchononespecifictopic has contributed richly to another, apparently unrelated area. Such a case is the work of Frederick Griffith, an English physician whose attempts to

2、prevent the disease pneumonia led to the identification of the material in cells that contains genetic information the information that determines an organisms characteristic structure. In the 1920s, Griffith was studying the bacterium Streptococcus pneumoniae, or pneumococcus, one of the organisms

3、that cause pneumonia in humans.He was trying to develop a vaccine against this devastating illness. Hewas working with two strains of the bacteria pneumococcus. Abacterial strain is a population of cells descended from a single parent cell; strains differ in one or more inherited characteristics. Gr

4、iffiths strains were designated S and R because, when grown in the laboratory, one produced shiny, smooth (S) colonies or groups of bacteria, and the other produced colonies that look rough .Thewordapparentlyinthepassageisclosestinmeaning.According to paragraph 1, Griffith experimented with strains

5、of the pneumococcus bacteria because he wanted to discover which of the followingAstrainofbacteriathatcouldbeusedtodevelopaHowbacterialstrainsdevelopedunderlaboratoryWhythestrainsofbacteriadifferedinWhichbacterialstrainsweremostinfectiousinAHewastryingtodevelopavaccineagainstthisdevastatingillnessHe

6、was workingwithtwostrainsofthebacteriapneumococcus. A。這一段講的就是介紹，此人原Paragraph 2：When the S strain was injected into mice, the mice became diseased. When the R strain was injected, the mice did not become diseased. Bacteria of the S strain are virulent (able to cause disease) because they are surround

7、ed by a protective jelly-like coating that prevents the mouses immune defense mechanisms from destroying the bacteria before they can multiply. The R strain lacks this coating.WhydoestheauthorprovidetheinformationthatTheRstrainlacksthisToprovideanexampleofvariationswithinstrainsofpneumococcusToexpla

8、inwhytheRstrainisnotabletocauseTo suggest that the R strain has other ways to defend itself from immune ToexplainwhymicebecamediseasedwheninjectedwiththeRstrain S B 對(duì)。Paragraph 3：With the hope of developing a vaccine against pneumonia, Griffith injected some mice with heat-killed S pneumococci. Thes

9、e heat-killed bacteria did not produce infection. Griffith assumed the mice would produce antibodies to the bacteria that would allowthemto fight the virulent form if they were exposed to it. However, when Griffith inoculated other mice with a mixture of living R bacteria and heat-killed S bacteria,

10、 to his astonishment, the mice became ill with pneumonia（加熱的S 被殺死應(yīng)不能致病，R 也不果兩者混合卻導(dǎo)致了致?。? When he examined blood fromthese mice, he founditfullofliving bacteria manywith characteristics of the virulent S strain. Griffith concluded that, in the presence of the dead S pneumococci, some of the living R

11、pneumococci had been transformed into virulent S-strain organisms.Thewordastonishmentinthepassageisclosestinmeaning.According to paragraph 3, why did Griffith conclude from his experiment injecting both R and S strains pneumococci into mice that some of the R strain bacteria transformed into disease

12、-causing S strain pneumococciAllthelivingbacteriahefoundinthebloodoftheinjectedmicewereSstrainHe already knew from earlier experiments that R strain pneumococci sometimes transform into S strain pneumococci.He could tell from examining the bacteria under a microscope that some individual pneumococci

13、 cells had characteristics of both the S and R strains.He observed living cells in the mices blood with S strain characteristics, but the only living cells injected were R strain pneumococci. Paragraph 4：Did this transformation of the bacteria depend on something the mouse did to the bacteria？No. It

14、 was shown that simply putting living R and heat-killed S bacteria together in a test tube yielded the same transformation. Next it was discovered that a cell-free extract of heat-killed S cells also transformed R cells. (A cell-free extract contains all the contents of cells, but no intact cells.)

15、This result demonstrated that some substance called at the time a transforming principle from the extract of S pneumococci could cause a heritable change (a change that could be passed on to future generations) in the affected R cells. From these observations, some scientists concluded that this tra

16、nsforming material carried heritable information, and thus was the genetic material that scientists had been searching for.Accordingtoparagraph4,whywasGriffithsexperimentrepeatedinatestToprovideadditionalsupportforthetransformationofR-strainintoS-strainTo establish whether or not the transformation

17、of R cells was caused by something the mouses body didTo determine why the S-strain pneumococci somehow survived if they were in the presence of the R-strainTotesttheresultsofaddingacell-freeextracttothe.Which of the sentences below best expresses the essential information in the highlighted sentenc

18、e in the passage Incorrect choices change the meaning in important ways or leave out essential information.This result showed that the chemical transforming principle in S pneumococci waspassed on to future generations of S pneumococci.After exposure to the cell-free extract from the S pneumococci,

19、R pneumococci strain cells acquired the ability to transform themselves into S pneumococci.The transformation of R cells by a cell-free extract of S pneumococci demonstrated the existence of a chemical transforming principle that brought about heritable change.This transformation showed that the cha

20、racteristics that the S pneumococci possess are superior to the characteristics of R pneumococci.C A S 到S，方向就不對(duì)。Paragraph 5：The identification of the transforming material was a crucial step in the history of biology, accomplished over a period of several years by Oswald Averyand his colleagues at w

21、hat is now Rockefeller University. They treated samples of the transforming extract in a variety of ways to destroydifferent types of substancesproteins, nucleic acids, carbohydrates, and lipids and testedthetreatedsamplesto seeiftheyhadretainedtransformingactivity.Theanswerwasalways the same: If th

22、e DNA(deoxyribo nucleic acid) in the extract was destroyed, transforming activity was lost; everything else could be eliminated without removing the transforming ability of the extract. As a final step, Avery, with Colin MacLeod and Maclyn McCarty, isolated virtually pure DNA from a sample of pneumo

23、coccal transforming extract and showed that it caused bacterial .According to paragraph 5, why did Oswald Avery and his colleagues treat the transforming extract in a variety of destructive waysTheyhopedtodestroythevirulentpartofthetransformingTheywantedtoidentifythesubstanceresponsibleforthetransfo

24、rmingTheywanted to identify which methods would destroy particular substances in the transforming Theyneededtodeterminewhichtreatmentsweremostsuccessfulindestroyingidentification of the transforming material was a crucial step in the history of biology, 此段就是thetransformingmaterial transforming trans

25、forming activity 有影響，則說明其起作用B.ThewordvirtuallyinthepassageisclosestinmeaningParagraph 6：In retrospect, the work of Avery, MacLeod, and McCarty, published in 1944, was a milestone in establishing that DNA is the genetic material. However, at the time, it had little impact on scientists view about the

26、 physical basis of inheritance. The genetic material had to encode all the information needed to specify an organism, and the chemical complexity and diversityofproteinswereknowntobeimpressive（impressive可以理解為足以引起人重視的）. So during the first half of the twentieth century, the hereditary material was ge

27、nerally assumed to be a protein. Nucleic acids, by contrast, were known to have only a few components and seemed too simple to carry such complex information.ThephraseInretrospectinthepassageisclosestinmeaningBygeneralInLookingPractically .According to paragraph 6, why did scientists continue to bel

28、ieve that the hereditary material was a proteinScientists thought that the research of Avery and his colleagues provided insufficient information about the nature of DNA.ScientistsbelievedthatonlyproteinswerecomplexenoughtocarrygeneticScientists thought Avery and his colleagues had little understand

29、ing of the physical basis of Scientistsignoredimportantmilestonesthatindicatedthechemicalcomplexityof【四箭齊發(fā)】解析：細(xì)節(jié)題。相關(guān)原文：Thegeneticmaterialhadtoencodealltheinformation needed to specifyan organism, and the chemical complexityand diversityof proteins were known to be impressive（impressive可以理解為足以引起人重視的）

30、. So during the first half of the twentieth century, the hereditarymaterialwas generallyassumed to be a protein. Nucleic acids, by contrast, were known to have only a few components and seemed too simple to carry such complex information.Nucleic acids chemical complexity and diversityprotein 有 chemi

31、cal complexity and diversity，可以作為遺傳物質(zhì)，B 為此說法的概括。.Which of the following can be inferred from the passage about the transformed R-strain TheyhadacquiredthegeneticinformationforproducingaprotectiveTheywereunabletocausetransformationinotherstrainsofInthepresenceofheat-killedR-strainbacteria,theylostthe

32、irTheydidnotmultiplyasquicklyasnontransformedcellsSRaprotectivecoating，第四段論證DNADNAR可以遺lost。.Look at the four squaresthat indicate where the following sentence could be added to the WherewouldthesentencebestClickonatoaddthesentencetothe.Dragyourchoicestothespaceswheretheybelong.Toreviewthepassage,clickonViewText. Answer ChoicesFrom the 1920s through 1944, researchers used pneumococcus bacteria to discover the properties of DNAbecause the bacteria was relatively simple, having only two strains.Frederick Griffith discovered that a nonvirulent strain of bacteria could be transforme