2013年GMAT考试阅读模拟试题及答案14
<p>2013年<span word="GMAT">GMAT</span>考试阅读模拟试题及答案汇总</p><p> <span word="Nearly">Nearly</span> <span word="a">a</span> <span word="century">century</span> <span word="ago">ago</span>, <span word="biologists">biologists</span> <span word="found">found</span> <span word="that">that</span> <span word="if">if</span> <span word="they">they</span> <span word="separated">separated</span> <span word="an">an</span> <span word="invertebrate">invertebrate</span> <span word="animal">animal</span> <span word="embryo">embryo</span> <span word="into">into</span> <span word="two">two</span> <span word="parts">parts</span> <span word="at">at</span> <span word="an">an</span> <span word="early">early</span> <span word="stage">stage</span> <span word="of">of</span> <span word="its">its</span> <span word="life">life</span>, <span word="it">it</span> <span word="would">would</span> <span word="survive">survive</span> <span word="and">and</span> <span word="develop">develop</span> <span word="as">as</span> <span word="two">two</span> <span word="normal">normal</span> <span word="embryos">embryos</span>. <span word="This">This</span> <span word="led">led</span> <span word="them">them</span> <span word="to">to</span> <span word="believe">believe</span> <span word="that">that</span> <span word="the">the</span> <span word="cells">cells</span> <span word="in">in</span> <span word="the">the</span> <span word="early">early</span> <span word="embryo">embryo</span> <span word="are">are</span> <span word="undetermined">undetermined</span> <span word="in">in</span> <span word="the">the</span> <span word="sense">sense</span> <span word="that">that</span> <span word="each">each</span> <span word="cell">cell</span> <span word="has">has</span> <span word="the">the</span> <span word="potential">potential</span> <span word="to">to</span> <span word="develop">develop</span> <span word="in">in</span> <span word="a">a</span> <span word="variety">variety</span> <span word="of">of</span> <span word="different">different</span> <span word="ways">ways</span>. <span word="Later">Later</span> <span word="biologists">biologists</span> <span word="found">found</span> <span word="that">that</span> <span word="the">the</span> <span word="situation">situation</span> <span word="was">was</span> <span word="not">not</span> <span word="so">so</span> <span word="simple">simple</span>. <span word="It">It</span> <span word="matters">matters</span> <span word="in">in</span> <span word="which">which</span> <span word="plane">plane</span> <span word="the">the</span> <span word="embryo">embryo</span> <span word="is">is</span> <span word="cut">cut</span>. <span word="If">If</span> <span word="it">it</span> <span word="is">is</span> <span word="cut">cut</span> <span word="in">in</span> <span word="a">a</span> <span word="plane">plane</span> <span word="different">different</span> <span word="from">from</span> <span word="the">the</span> <span word="one">one</span> <span word="used">used</span> <span word="by">by</span> <span word="the">the</span> <span word="early">early</span> <span word="investigators">investigators</span>, <span word="it">it</span> <span word="will">will</span> <span word="not">not</span> <span word="form">form</span> <span word="two">two</span> <span word="whole">whole</span> <span word="embryos">embryos</span>.</p><p> <span word="A">A</span> <span word="debate">debate</span> <span word="arose">arose</span> <span word="over">over</span> <span word="what">what</span> <span word="exactly">exactly</span> <span word="was">was</span> <span word="happening">happening</span>. <span word="Which">Which</span> <span word="embryo">embryo</span> <span word="cells">cells</span> <span word="are">are</span> <span word="determined">determined</span>, <span word="just">just</span> <span word="when">when</span> <span word="do">do</span> <span word="they">they</span> <span word="become">become</span> <span word="irreversibly">irreversibly</span> <span word="committed">committed</span> <span word="to">to</span> <span word="their">their</span> <span word="fates">fates</span>, <span word="and">and</span> <span word="what">what</span> <span word="are">are</span> <span word="the">the</span> “<span word="morphogenetic">morphogenetic</span> <span word="determinants">determinants</span>” <span word="that">that</span> <span word="tell">tell</span> <span word="a">a</span> <span word="cell">cell</span> <span word="what">what</span> <span word="to">to</span> <span word="become">become</span>? <span word="But">But</span> <span word="the">the</span> <span word="debate">debate</span> <span word="could">could</span> <span word="not">not</span> <span word="be">be</span> <span word="resolved">resolved</span> <span word="because">because</span> <span word="no">no</span> <span word="one">one</span> <span word="was">was</span> <span word="able">able</span> <span word="to">to</span> <span word="ask">ask</span> <span word="the">the</span> <span word="crucial">crucial</span> <span word="questions">questions</span> <span word="in">in</span> <span word="a">a</span> <span word="form">form</span> <span word="in">in</span> <span word="which">which</span> <span word="they">they</span> <span word="could">could</span> <span word="be">be</span> <span word="pursued">pursued</span> <span word="productively">productively</span>. <span word="Recent">Recent</span> <span word="discoveries">discoveries</span> <span word="in">in</span> <span word="molecular">molecular</span> <span word="biology">biology</span>, <span word="however">however</span>, <span word="have">have</span> <span word="opened">opened</span> <span word="up">up</span> <span word="prospects">prospects</span> <span word="for">for</span> <span word="a">a</span> <span word="resolution">resolution</span> <span word="of">of</span> <span word="the">the</span> <span word="debate">debate</span>. <span word="Now">Now</span> <span word="investigators">investigators</span> <span word="think">think</span> <span word="they">they</span> <span word="know">know</span> <span word="at">at</span> <span word="least">least</span> <span word="some">some</span> <span word="of">of</span> <span word="the">the</span> <span word="molecules">molecules</span> <span word="that">that</span> <span word="act">act</span> <span word="as">as</span> <span word="morphogenetic">morphogenetic</span> <span word="determinants">determinants</span> <span word="in">in</span> <span word="early">early</span> <span word="development">development</span>. <span word="They">They</span> <span word="have">have</span> <span word="been">been</span> <span word="able">able</span> <span word="to">to</span> <span word="show">show</span> <span word="that">that</span>, <span word="in">in</span> <span word="a">a</span> <span word="sense">sense</span>, <span word="cell">cell</span> <span word="determination">determination</span> <span word="begins">begins</span> <span word="even">even</span> <span word="before">before</span> <span word="an">an</span> <span word="egg">egg</span> <span word="is">is</span> <span word="fertilized">fertilized</span>.</p><p> <span word="Studying">Studying</span> <span word="sea">sea</span> <span word="urchins">urchins</span> (<span word="any">any</span> <span word="of">of</span> <span word="numerous">numerous</span> <span word="echinoderms">echinoderms</span> (<span word="class">class</span> <span word="Echinoidea">Echinoidea</span>) <span word="that">that</span> <span word="are">are</span> <span word="usually">usually</span> <span word="enclosed">enclosed</span> <span word="in">in</span> <span word="thin">thin</span> <span word="brittle">brittle</span> <span word="globular">globular</span> <span word="tests">tests</span> <span word="covered">covered</span> <span word="with">with</span> <span word="movable">movable</span> <span word="spines">spines</span>海胆), <span word="biologist">biologist</span> <span word="Paul">Paul</span> <span word="Gross">Gross</span> <span word="found">found</span> <span word="that">that</span> <span word="an">an</span> <span word="unfertilized">unfertilized</span> <span word="egg">egg</span> <span word="contains">contains</span> <span word="substances">substances</span> <span word="that">that</span> <span word="function">function</span> <span word="as">as</span> <span word="morphogenetic">morphogenetic</span> <span word="determinants">determinants</span>. <span word="They">They</span> <span word="are">are</span> <span word="located">located</span> <span word="in">in</span> <span word="the">the</span> <span word="cytoplasm">cytoplasm</span> <span word="of">of</span> <span word="the">the</span> <span word="egg">egg</span> <span word="cell">cell</span>; <span word="i">i</span>.<span word="e">e</span>., <span word="in">in</span> <span word="that">that</span> <span word="part">part</span> <span word="of">of</span> <span word="the">the</span> <span word="cell">cell</span>’<span word="s">s</span> <span word="protoplasm">protoplasm</span> <span word="that">that</span> <span word="lies">lies</span> <span word="outside">outside</span> <span word="of">of</span> <span word="the">the</span> <span word="nucleus">nucleus</span>. <span word="In">In</span> <span word="the">the</span> <span word="unfertilized">unfertilized</span> <span word="egg">egg</span>, <span word="the">the</span> <span word="substances">substances</span> <span word="are">are</span> <span word="inactive">inactive</span> <span word="and">and</span> <span word="are">are</span> <span word="not">not</span> <span word="distributed">distributed</span> <span word="homogeneously">homogeneously</span>. <span word="When">When</span> <span word="the">the</span> <span word="egg">egg</span> <span word="is">is</span> <span word="fertilized">fertilized</span>, <span word="the">the</span> <span word="substances">substances</span> <span word="become">become</span> <span word="active">active</span> <span word="and">and</span>, <span word="presumably">presumably</span>, <span word="govern">govern</span> <span word="the">the</span> <span word="behavior">behavior</span> <span word="of">of</span> <span word="the">the</span> <span word="genes">genes</span> <span word="they">they</span> <span word="interact">interact</span> <span word="with">with</span>. <span word="Since">Since</span> <span word="the">the</span> <span word="substances">substances</span> <span word="are">are</span> <span word="unevenly">unevenly</span> <span word="distributed">distributed</span> <span word="in">in</span> <span word="the">the</span> <span word="egg">egg</span>, <span word="when">when</span> <span word="the">the</span> <span word="fertilized">fertilized</span> <span word="egg">egg</span> <span word="divides">divides</span>, <span word="the">the</span> <span word="resulting">resulting</span> <span word="cells">cells</span> <span word="are">are</span> <span word="different">different</span> <span word="from">from</span> <span word="the">the</span> <span word="start">start</span> <span word="and">and</span> <span word="so">so</span> <span word="can">can</span> <span word="be">be</span> <span word="qualitatively">qualitatively</span> <span word="different">different</span> <span word="in">in</span> <span word="their">their</span> <span word="own">own</span> <span word="gene">gene</span> <span word="activity">activity</span>.</p>
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