|
|
考研英语阅读题源来源广泛，取自《经济学人》、《纽约时报》、《新闻周刊》、《卫报》、《Nature》、《华盛顿邮报》、《The Scientist》等等【了解更多题源】，因此考生可以多关注一下此类文章。下面新东方在线分享一些考过的题源文章，并附上详细解析，本阶段复习，大家可以看看。
From TIME
By Alice Park
Jan. 9,2006
Is Snuppy the Puppy for Real?
With Hwang's scientific credibility in shambles, the status of the world's
most famous dog hangs in the balance. The embattled scientist maintains that
Snuppy is the world's first canine clone, and he even hired an independent
Korean DNA lab, Human Pass Inc, to verify that assertion. The verdict: Human
Pass CEO Seung Jae Rhee told TIME last week, "There is no dispute about these
results, and so I am 100% certain on Snuppy's authenticity." But since Human
Pass is in essence working for Hwang, that's hardly good enough for the
investigative panel at Seoul National University, which is carrying out
independent tests, or for the editors of Nature, who have ordered an
investigation.
If Snuppy really was cloned from the ear cell of a 3-year-old male Afghan
named Tai, it shouldn't be tough to prove, even to those outside investigators. As long
as they have tissue samples from both the clone and the parent, they should be able to
determine whether DNA in the nuclei of both animals' cells is identical-the first hallmark of
a true clone. Ian Wilmut, the Scottish scientist who created Dolly the sheep in 1996, had
to provide such samples to prove to skeptics that he had created history's first mammalian
clone.
Even with the controversy raging over his stem-cell paper, Hwang could have
forestalled some of the questions about Snuppy if he had offered one additional bit of
confirming proof in his original paper in Nature. That piece of critical evidence
comes from the animals' mitochondria, tiny energy-producing structures within each cell. While most
of a mammal's DNA resides in the nucleus, there's also some in the mitochondria. (Nuclear
DNA forms the animal's basic genetic blueprint; mitochondrial DNA contains
instructions for making proteins involved in various metabolic functions within the cell. )
Mitochondrial DNA is passed down from the mother as gart of the egg's
genetic contribution. Identical twins, for example, have the same nuclear and
mitochondrial DNA, since they're produced when a single egg is fertilized and the resulting
embryo splits in two. With a clone, the situation is different. Because the cloning process that
Hwang says he used to create Snuppy involves two dogs-one for the nucleus and another for the
egg-Snuppy's mitochondrial DNA should not match Tai's. That's what Rhee's scientists say
they've found and what Hwang undoubtedly hopes the university and Nature will find as
well. Final, ironclad proof of Snuppy’s provenance would involve showing that the dog's
mitochondrial DNA matches that of his egg donor .It's not clear, however, whether that test
is being done.
|
|
发表于 2017-8-6 16:20:41