2016届高考英语精品专题必做练习：阅读理解（5）
<p> <span word="A">A</span></p><p> <span word="Can">Can</span> <span word="people">people</span> <span word="change">change</span> <span word="their">their</span> <span word="skin">skin</span> <span word="color">color</span> <span word="without">without</span> <span word="suffering">suffering</span> <span word="like">like</span> <span word="pop">pop</span> <span word="king">king</span> <span word="Michael">Michael</span> <span word="Jackson">Jackson</span>？<span word="Perhaps">Perhaps</span> <span word="yes">yes</span>.<span word="Scientists">Scientists</span> <span word="have">have</span> <span word="found">found</span> <span word="the">the</span> <span word="gene">gene</span> <span word="that">that</span> <span word="determines">determines</span> <span word="skin">skin</span> <span word="color">color</span>.</p><p> <span word="The">The</span> <span word="gene">gene</span> <span word="comes">comes</span> <span word="in">in</span> <span word="two">two</span> <span word="versions">versions</span>，<span word="one">one</span> <span word="of">of</span> <span word="which">which</span> <span word="is">is</span> <span word="found">found</span> <span word="in">in</span> 99 <span word="per">per</span> <span word="cent">cent</span> <span word="of">of</span> <span word="Europeans">Europeans</span>.<span word="The">The</span> <span word="other">other</span> <span word="is">is</span> <span word="found">found</span> <span word="in">in</span> 93 <span word="to">to</span> 100 <span word="per">per</span> <span word="cent">cent</span> <span word="of">of</span> <span word="Africans">Africans</span>，<span word="researchers">researchers</span></p><p> <span word="at">at</span></p><p> <span word="the">the</span></p><p> <span word="Pennsylvania">Pennsylvania</span> <span word="State">State</span> <span word="University">University</span> <span word="report">report</span> <span word="in">in</span> <span word="the">the</span> <span word="latest">latest</span> <span word="issue">issue</span> <span word="of">of</span> <span word="Science">Science</span>.</p><p> <span word="Scientists">Scientists</span> <span word="have">have</span> <span word="changed">changed</span> <span word="the">the</span> <span word="color">color</span> <span word="of">of</span> <span word="a">a</span> <span word="dark">dark</span><span word="striped">striped</span> <span word="zebrafish">zebrafish</span> (斑马鱼) <span word="to">to</span> <span word="gold">gold</span> <span word="by">by</span> <span word="inserting">inserting</span> <span word="a">a</span> <span word="version">version</span> <span word="of">of</span> <span word="the">the</span> <span word="pigment">pigment</span> (色素) <span word="gene">gene</span> <span word="into">into</span> <span word="a">a</span> <span word="young">young</span> <span word="fish">fish</span>.<span word="As">As</span> <span word="with">with</span> <span word="humans">humans</span>，<span word="the">the</span> <span word="skin">skin</span> <span word="color">color</span> <span word="of">of</span> <span word="zebrafish">zebrafish</span> <span word="is">is</span> <span word="determined">determined</span> <span word="by">by</span> <span word="pigment">pigment</span> <span word="cells">cells</span>，<span word="which">which</span> <span word="contain">contain</span> <span word="melanin">melanin</span> (黑色素)．<span word="The">The</span> <span word="number">number</span>，<span word="size">size</span> <span word="and">and</span> <span word="darkness">darkness</span> <span word="of">of</span> <span word="melanin">melanin</span> <span word="per">per</span> <span word="pigment">pigment</span> <span word="cell">cell</span> <span word="determine">determine</span> <span word="skin">skin</span> <span word="color">color</span>.</p><p> <span word="It">It</span> <span word="appears">appears</span> <span word="that">that</span>，<span word="like">like</span> <span word="the">the</span> <span word="golden">golden</span> <span word="zebrafish">zebrafish</span>，<span word="light">light</span><span word="skinned">skinned</span> <span word="Europeans">Europeans</span> <span word="also">also</span> <span word="have">have</span> <span word="a">a</span> <span word="mutation">mutation</span> (变异) <span word="in">in</span> <span word="the">the</span> <span word="gene">gene</span> <span word="for">for</span> <span word="melanin">melanin</span> <span word="production">production</span>.<span word="This">This</span> <span word="results">results</span> <span word="in">in</span> <span word="less">less</span> <span word="pigmented">pigmented</span> <span word="skin">skin</span>.</p><p> <span word="However">However</span>，<span word="Keith">Keith</span> <span word="Cheng">Cheng</span>，<span word="leader">leader</span> <span word="of">of</span> <span word="the">the</span> <span word="research">research</span> <span word="team">team</span>，<span word="points">points</span> <span word="out">out</span> <span word="that">that</span> <span word="the">the</span> <span word="mutation">mutation</span> <span word="is">is</span> <span word="different">different</span> <span word="in">in</span> <span word="human">human</span> <span word="and">and</span> <span word="zebrafish">zebrafish</span> <span word="genes">genes</span>.</p><p> <span word="Humans">Humans</span> <span word="acquired">acquired</span> <span word="dark">dark</span> <span word="skin">skin</span> <span word="in">in</span> <span word="Africa">Africa</span> <span word="about">about</span> 1.5 <span word="million">million</span> <span word="years">years</span> <span word="ago">ago</span> <span word="to">to</span> <span word="protect">protect</span> <span word="bodies">bodies</span> <span word="from">from</span> <span word="ultra">ultra</span><span word="violet">violet</span> <span word="rays">rays</span> <span word="of">of</span> <span word="the">the</span> <span word="sun">sun</span>，<span word="which">which</span> <span word="can">can</span> <span word="cause">cause</span> <span word="skin">skin</span> <span word="cancer">cancer</span>.</p><p> <span word="But">But</span> <span word="when">when</span> <span word="modern">modern</span> <span word="humans">humans</span> <span word="leave">leave</span> <span word="Africa">Africa</span> <span word="to">to</span> <span word="live">live</span> <span word="in">in</span> <span word="northern">northern</span> <span word="latitudes">latitudes</span>，<span word="they">they</span> <span word="need">need</span> <span word="more">more</span> <span word="sunlight">sunlight</span> <span word="on">on</span> <span word="their">their</span> <span word="skin">skin</span> <span word="to">to</span> <span word="produce">produce</span> <span word="vitamin">vitamin</span> <span word="D">D</span>．<span word="So">So</span> <span word="the">the</span> <span word="related">related</span> <span word="gene">gene</span> <span word="changes">changes</span>，<span word="according">according</span> <span word="to">to</span> <span word="Cheng">Cheng</span>.</p>
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