名师GRE阅读难句背诵实例（九）
<p> 40.<span word="It">It</span> <span word="is">is</span> <span word="possible">possible</span> <span word="to">to</span> <span word="make">make</span> <span word="specific">specific</span> <span word="complementary">complementary</span> <span word="DNAsthat">DNAsthat</span> <span word="can">can</span> <span word="serve">serve</span> <span word="as">as</span> <span word="molecular">molecular</span> <span word="probes">probes</span> <span word="to">to</span> <span word="seek">seek</span> <span word="out">out</span> <span word="the">the</span> <span word="messengerRNAs">messengerRNAs</span> <span word="of">of</span> <span word="the">the</span> <span word="peptide">peptide</span> <span word="hormones">hormones</span>. <span word="If">If</span> <span word="brain">brain</span> <span word="cells">cells</span> <span word="are">are</span> <span word="making">making</span> <span word="thehormones">thehormones</span>，<span word="the">the</span> <span word="cells">cells</span> <span word="will">will</span> <span word="contain">contain</span> <span word="these">these</span> <span word="MrnaS">MrnaS</span>. <span word="If">If</span> <span word="the">the</span> <span word="products">products</span> <span word="the">the</span> <span word="braincells">braincells</span> <span word="make">make</span> <span word="resemble">resemble</span> <span word="the">the</span> <span word="hormones">hormones</span> <span word="but">but</span> <span word="are">are</span> <span word="not">not</span> <span word="identical">identical</span> <span word="to">to</span> <span word="them">them</span>，<span word="then">then</span> <span word="thecDNAs">thecDNAs</span> <span word="should">should</span> <span word="still">still</span> <span word="bind">bind</span> <span word="to">to</span> <span word="these">these</span> <span word="mRNAs">mRNAs</span>，<span word="but">but</span> <span word="should">should</span> <span word="not">not</span> <span word="bind">bind</span> <span word="astightly">astightly</span> <span word="as">as</span> <span word="they">they</span> <span word="would">would</span> <span word="to">to</span> <span word="mRNAs">mRNAs</span> <span word="for">for</span> <span word="the">the</span> <span word="true">true</span> <span word="hormones">hormones</span>.</p><p> 科学家可以制造出特异的互补<span word="DNAs">DNAs</span>，以此作为分子探子，探觅出肽激素的信使<span word="RNAs">RNAs</span>。如果大脑正在制造着肽激素，则细胞就会含有这些信使<span word="RNAs">RNAs</span>.假若细胞所制造的产品类似于肽激素但并非与这些肽激素全然相同，那么，互补<span word="cDNAs">cDNAs</span>应仍然和这些信使<span word="mDNAs">mDNAs</span>粘结的程度。含有这些<span word="mRNAs">mRNAs</span>的脑细胞然后就可以被分离开来，研究者可对其信使<span word="RNAs">RNAs</span>进行解码，以确定它们的蛋白质产品究竟是什么，并确定这些蛋白质产品在何种程度上类似于真正的肽激素。</p><p> 41.<span word="The">The</span> <span word="molecular">molecular</span> <span word="approach">approach</span> <span word="to">to</span> <span word="detecting">detecting</span> <span word="peptide">peptide</span> <span word="hormones">hormones</span> <span word="using">using</span> <span word="cDNAprobes">cDNAprobes</span> <span word="should">should</span> <span word="also">also</span> <span word="be">be</span> <span word="much">much</span> <span word="faster">faster</span> <span word="than">than</span> <span word="the">the</span> <span word="immunological">immunological</span> <span word="method">method</span> <span word="becauseit">becauseit</span> <span word="can">can</span> <span word="take">take</span> <span word="years">years</span> <span word="of">of</span> <span word="tedious">tedious</span> <span word="purifications">purifications</span> <span word="to">to</span> <span word="isolate">isolate</span> <span word="peptide">peptide</span> <span word="hormonesand">hormonesand</span> <span word="then">then</span> <span word="develop">develop</span> <span word="antiserums">antiserums</span> <span word="to">to</span> <span word="them">them</span>.</p><p> 采用<span word="cDNA">cDNA</span>探子来测定肽激素的这一分子生物学方法同时也应该比免疫学的方法速度来得快，因为对于免疫的方法来说，需耗费好几年枯燥的提纯进程，方能将肽素分离了出来，然后再培养出针对它们的抗血清。</p>
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