gre考试阅读真题解析(A)
<p> <span word="The">The</span> <span word="more">more</span> <span word="that">that</span> <span word="is">is</span> <span word="discovered">discovered</span> <span word="about">about</span> <span word="the">the</span> <span word="intricate">intricate</span> <span word="organization">organization</span> <span word="of">of</span> <span word="the">the</span> <span word="nervous">nervous</span> <span word="system">system</span>, <span word="the">the</span> <span word="more">more</span> <span word="it">it</span> <span word="seems">seems</span> <span word="remarkable">remarkable</span> <span word="that">that</span> <span word="genes">genes</span> <span word="can">can</span> <span word="successfully">successfully</span> <span word="specify">specify</span> <span word="the">the</span> <span word="development">development</span> <span word="of">of</span> <span word="that">that</span> <span word="system">system</span>. <span word="Human">Human</span> <span word="genes">genes</span> <span word="contain">contain</span> <span word="too">too</span> <span word="little">little</span> <span word="information">information</span> <span word="even">even</span> <span word="to">to</span> <span word="specify">specify</span> <span word="which">which</span> <span word="hemisphere">hemisphere</span> <span word="of">of</span> <span word="the">the</span> <span word="brain">brain</span> <span word="each">each</span> <span word="of">of</span> <span word="a">a</span> <span word="humans">humans</span> 1011 <span word="neurons">neurons</span> <span word="should">should</span> <span word="occupy">occupy</span>, <span word="let">let</span> <span word="alone">alone</span> <span word="the">the</span> <span word="hundreds">hundreds</span> <span word="of">of</span> <span word="connections">connections</span> <span word="that">that</span> <span word="each">each</span> <span word="neuron">neuron</span> <span word="makes">makes</span>. <span word="For">For</span> <span word="such">such</span> <span word="reasons">reasons</span>, <span word="we">we</span> <span word="can">can</span> <span word="assume">assume</span> <span word="that">that</span> <span word="there">there</span> <span word="must">must</span> <span word="be">be</span> <span word="an">an</span> <span word="important">important</span> <span word="random">random</span> <span word="factor">factor</span> <span word="in">in</span> <span word="neural">neural</span> <span word="development">development</span>, <span word="and">and</span> <span word="in">in</span> <span word="particular">particular</span>, <span word="that">that</span> <span word="errors">errors</span> <span word="must">must</span> <span word="and">and</span> <span word="do">do</span> <span word="occur">occur</span> <span word="in">in</span> <span word="the">the</span> <span word="development">development</span> <span word="of">of</span> <span word="all">all</span> <span word="normal">normal</span> <span word="brains">brains</span>.</p><p> <span word="The">The</span> <span word="most">most</span> <span word="vivid">vivid</span> <span word="expression">expression</span> <span word="of">of</span> <span word="such">such</span> <span word="errors">errors</span> <span word="occurs">occurs</span> <span word="in">in</span> <span word="genetically">genetically</span> <span word="identical">identical</span> <span word="organisms">organisms</span>. <span word="Even">Even</span> <span word="when">when</span> <span word="reared">reared</span> <span word="under">under</span> <span word="the">the</span> <span word="same">same</span> <span word="conditions">conditions</span>, <span word="isogenic">isogenic</span> <span word="organisms">organisms</span> <span word="are">are</span> <span word="rarely">rarely</span> <span word="exact">exact</span> <span word="copies">copies</span> <span word="of">of</span> <span word="one">one</span> <span word="another">another</span>, <span word="and">and</span> <span word="their">their</span> <span word="differences">differences</span> <span word="have">have</span> <span word="revealed">revealed</span> <span word="much">much</span> <span word="about">about</span> <span word="the">the</span> <span word="random">random</span> <span word="variations">variations</span> <span word="that">that</span> <span word="result">result</span> <span word="from">from</span> <span word="an">an</span> <span word="organisms">organisms</span> <span word="limited">limited</span> <span word="supply">supply</span> <span word="of">of</span> <span word="genetic">genetic</span> <span word="information">information</span>. <span word="In">In</span> <span word="isogenic">isogenic</span> <span word="Daphniae">Daphniae</span>, <span word="for">for</span> <span word="example">example</span>, <span word="even">even</span> <span word="though">though</span> <span word="the">the</span> <span word="position">position</span>, <span word="size">size</span>, <span word="and">and</span> <span word="branching">branching</span> <span word="pattern">pattern</span> <span word="of">of</span> <span word="each">each</span> <span word="optic">optic</span> <span word="neuron">neuron</span> <span word="are">are</span> <span word="remarkably">remarkably</span> <span word="constant">constant</span>, <span word="there">there</span> <span word="is">is</span> <span word="some">some</span> <span word="variability">variability</span> <span word="in">in</span> <span word="connectivity">connectivity</span>, <span word="and">and</span> <span word="the">the</span> <span word="number">number</span> <span word="of">of</span> <span word="synapses">synapses</span> <span word="varies">varies</span> <span word="greatly">greatly</span>. <span word="This">This</span> <span word="variability">variability</span> <span word="is">is</span> <span word="probably">probably</span> <span word="the">the</span> <span word="result">result</span> <span word="of">of</span> <span word="random">random</span> <span word="scatter">scatter</span> <span word="beyond">beyond</span> <span word="the">the</span> <span word="resolution">resolution</span> <span word="of">of</span> <span word="genetic">genetic</span> <span word="control">control</span> <span word="and">and</span> <span word="is">is</span> <span word="best">best</span> <span word="termed">termed</span> <span word="imprecision">imprecision</span>, <span word="since">since</span> <span word="its">its</span> <span word="converse">converse</span>, <span word="the">the</span> <span word="degree">degree</span> <span word="of">of</span> <span word="clustering">clustering</span> <span word="about">about</span> <span word="a">a</span> <span word="mean">mean</span>, <span word="is">is</span> <span word="conventionally">conventionally</span>, <span word="called">called</span> <span word="precision">precision</span>.</p><p> <span word="Imprecision">Imprecision</span> <span word="should">should</span> <span word="be">be</span> <span word="distinguished">distinguished</span> <span word="from">from</span> <span word="developmental">developmental</span> <span word="mistakes">mistakes</span>: <span word="wrongly">wrongly</span> <span word="migrated">migrated</span> <span word="neurons">neurons</span>, <span word="incorrect">incorrect</span> <span word="connections">connections</span>, <span word="and">and</span> <span word="the">the</span> <span word="like">like</span>. <span word="To">To</span> <span word="use">use</span> <span word="a">a</span> <span word="computer">computer</span> <span word="analogy">analogy</span>, <span word="minor">minor</span> <span word="rounding">rounding</span>-<span word="off">off</span> <span word="errors">errors</span> <span word="occur">occur</span> <span word="universally">universally</span> <span word="and">and</span> <span word="are">are</span> <span word="analogous">analogous</span> <span word="to">to</span> <span word="imprecision">imprecision</span>, <span word="but">but</span> <span word="occasionally">occasionally</span> <span word="a">a</span> <span word="binary">binary</span> <span word="digit">digit</span> <span word="is">is</span> <span word="incorrectly">incorrectly</span> <span word="transmitted">transmitted</span>, <span word="perhaps">perhaps</span> <span word="ruining">ruining</span> <span word="a">a</span> <span word="calculation">calculation</span>, <span word="and">and</span> <span word="this">this</span> <span word="incorrect">incorrect</span> <span word="transmission">transmission</span> <span word="is">is</span> <span word="analogous">analogous</span> <span word="to">to</span> <span word="a">a</span> <span word="developmental">developmental</span> <span word="mistake">mistake</span>. <span word="Thus">Thus</span>, <span word="imprecision">imprecision</span> <span word="is">is</span> <span word="a">a</span> <span word="form">form</span> <span word="of">of</span> <span word="inaccuracy">inaccuracy</span> <span word="inherent">inherent</span> <span word="within">within</span> <span word="the">the</span> <span word="limits">limits</span> <span word="of">of</span> <span word="design">design</span>, <span word="but">but</span> <span word="mistakes">mistakes</span> <span word="are">are</span> <span word="forms">forms</span> <span word="of">of</span> <span word="gross">gross</span> <span word="fallibility">fallibility</span>.</p>
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