科学家朝克隆人又迈近一步
<p><span word="Scientists">Scientists</span> <span word="have">have</span> <span word="used">used</span> <span word="cloning">cloning</span> <span word="technology">technology</span> <span word="to">to</span> <span word="transform">transform</span> <span word="human">human</span> <span word="skin">skin</span> <span word="cells">cells</span> <span word="into">into</span> <span word="embryonic">embryonic</span> <span word="stem">stem</span> <span word="cells">cells</span>, <span word="an">an</span> <span word="experiment">experiment</span> <span word="that">that</span> <span word="may">may</span> <span word="revive">revive</span> <span word="the">the</span> <span word="controversy">controversy</span> <span word="over">over</span> <span word="human">human</span> <span word="cloning">cloning</span>.</p><p>科学家利用克隆技术将人体皮肤细胞转化为胚胎干细胞。这一实验可能再次引发有关克隆人的争论。</p><p><span word="The">The</span> <span word="researchers">researchers</span> <span word="stopped">stopped</span> <span word="well">well</span> <span word="short">short</span> <span word="of">of</span> <span word="creating">creating</span> <span word="a">a</span> <span word="human">human</span> <span word="clone">clone</span>. <span word="But">But</span> <span word="they">they</span> <span word="showed">showed</span>, <span word="for">for</span> <span word="the">the</span> <span word="first">first</span> <span word="time">time</span>, <span word="that">that</span> <span word="it">it</span> <span word="is">is</span> <span word="possible">possible</span> <span word="to">to</span> <span word="create">create</span> <span word="cloned">cloned</span> <span word="embryonic">embryonic</span> <span word="stem">stem</span> <span word="cells">cells</span> <span word="that">that</span> <span word="are">are</span> <span word="genetically">genetically</span> <span word="identical">identical</span> <span word="to">to</span> <span word="the">the</span> <span word="person">person</span> <span word="from">from</span> <span word="whom">whom</span> <span word="they">they</span> <span word="are">are</span> <span word="derived">derived</span>.</p><p>研究人员的成果距创造出克隆人还很遥远，但他们首次表明，创造出同人类基因完全相同的克隆胚胎干细胞是可能的。这些胚胎干细胞就来自人类。</p><p><span word="These">These</span> <span word="stem">stem</span> <span word="cells">cells</span> <span word="can">can</span> <span word="go">go</span> <span word="on">on</span> <span word="to">to</span> <span word="differentiate">differentiate</span> <span word="into">into</span> <span word="heart">heart</span>, <span word="nerve">nerve</span>, <span word="muscle">muscle</span>, <span word="bone">bone</span> <span word="and">and</span> <span word="all">all</span> <span word="the">the</span> <span word="other">other</span> <span word="tissue">tissue</span> <span word="types">types</span> <span word="that">that</span> <span word="make">make</span> <span word="up">up</span> <span word="a">a</span> <span word="human">human</span> <span word="body">body</span>.</p><p>这些干细胞可以分化成心脏、神经、肌肉、骨骼和其它所有组成人体的组织型。</p><p><span word="Since">Since</span> <span word="the">the</span> <span word="birth">birth</span> <span word="of">of</span> <span word="Dolly">Dolly</span> <span word="the">the</span> <span word="sheep">sheep</span> <span word="in">in</span> 1996, <span word="researchers">researchers</span> <span word="have">have</span> <span word="cloned">cloned</span> <span word="about">about</span> 20 <span word="different">different</span> <span word="species">species</span>, <span word="including">including</span> <span word="rabbits">rabbits</span>, <span word="goats">goats</span>, <span word="cows">cows</span> <span word="and">and</span> <span word="cats">cats</span>. <span word="Yet">Yet</span> <span word="they">they</span> <span word="so">so</span> <span word="far">far</span> <span word="have">have</span> <span word="been">been</span> <span word="unable">unable</span> <span word="to">to</span> <span word="create">create</span> <span word="biologically">biologically</span> <span word="identical">identical</span> <span word="copies">copies</span> <span word="of">of</span> <span word="any">any</span> <span word="monkey">monkey</span> <span word="or">or</span> <span word="primate">primate</span>, <span word="including">including</span> <span word="humans">humans</span>, <span word="possibly">possibly</span> <span word="because">because</span> <span word="their">their</span> <span word="reproductive">reproductive</span> <span word="biology">biology</span> <span word="is">is</span> <span word="more">more</span> <span word="complicated">complicated</span>.</p><p>自1996年克隆绵羊多莉(<span word="Dolly">Dolly</span>)诞生以来，研究人员已经克隆出大约20个不同物种，包括兔子、山羊、奶牛和猫。然而研究人员至今无法创造出在生物性上完全相同的猴子或灵长类动物（包括人类）的克隆体，原因可能在于这些生物的生殖生物学更复杂。</p>
页:
[1]