Everylivingcellcontainsgenes.Theyaretoosmalltobeseeninamicroscopebuttheyareveryimportant.Eachsetofgenesinthebodycontainsalltheinstructionsneededtomakeahumanbeing.Somegenesdeterminehaircolor.Somedeterminetheshapeofanose.Somegeneshelpdetermineyourheightandevenyourweight.
GenesaremadeofachemicalcalledDNA-thelettersstandfordeoxyribonucleicacid(脱氧核糖核酸).Intheearly1950'stwoscientistsFrancisCrickandJamesWatsonfiguredouthowthepartsofDNAfittogether.OncescientistsunderstoodthisstructureitbecamepossibletotakepiecesofDNAapartandputthemtogetherinnewways.Newkindsofgenescouldbemadeinthismanner.
Scientistshavestudiedthegenesofmanyplantsandanimals.Theyhaveworkedoutwhichgenesaffectthecolorofatomatoandthethicknessofitsskin.WorkingoutwhichgenesdeterminewhichfeaturesiscalledgeneticmappingscientistshavebeguntheHumanGenomeProjectanambitiousefforttomapallthegenesinthehumanbody.
Somegenesmaybedefective(有缺陷的).Forexamplesomethingmightbewrongwiththegenethatmakesbloodclot(凝聚).Ababybornwiththisdefectivegenecouldsufferserioushemorrhages(出血)orevenbleedtodeathbecausehisorherbloodfailstoclot.Ifscientistseverlearnhowtomapallthegenesinourbodiestheycandeterminewhetherornotanunbornchildhasanydefectivegenes.Theymightevendiscoverhowtotreatthesegenesbeforethechildisborn.
1.WhatwastheachievementofFrancisCrickandJamesWatson?
A.Theydiscoveredwhypeoplehavedifferenthaircolors.
B.Theylearnedthatsomepeoplebleedforlongperiodsoftime.
C.Theylookedathumancellsunderthemicroscope.
D.TheyworkedoutthestructureofDNA.
2.Whatisthemainideaofthispassage?
A.Defectivegenescanneverberepaired.
B.Genesaretoosmalltobeseenthroughamicroscope.
C.Geneshelpscientistsunderstandhowlivingthingsdeveloptheircharacteristics.
D.TheHumanGenomeProjectmayexplaintheroleofeverygeneinthebody.
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