单选题
Gene therapy and gene-based drugs are two ways we
could benefit from our growing mastery of genetic science. But there will be
others as well. Here is one of the remarkable therapies on the cutting edge of
genetic research that could make their way into mainstream medicine in the
coming years. While it's true that just about every cell in the
body has the instructions to make a complete human, most of those instructions
are inactivated, and with good reason: the last thing you want for your brain
cells is to start churning out stomach acid or your nose to turn into a kidney.
The only time cells truly have the potential to turn into any and all body parts
is very early in a pregnancy, when so-called stem cells haven't begun to
specialize. Yet this untapped potential could be a terrific
boon to medicine. Most diseases involve the death of healthy cells--brain cells
in Alzheimer's, cardiac cells in heart disease, pancreatic cells in diabetes, to
name a few. If doctors could isolate stem cells, then direct their growth, they
might be able to furnish patients with healthy replacement tissue.
It was incredibly difficult, but last fall scientists at the University
of Wisconsin managed to isolate stem cells and get them to grow into neural,
gut, muscle and bone cells. The process still can't be controlled, and may have
unforeseen limitations. But if efforts to understand and master stem-cell
development prove successful, doctors will have a therapeutic tool of incredible
power. The same applies to cloning, which is really just the
other side of the coin; true cloning, as first shown with the sheep Dolly two
years ago, involves taking a developed cell and reactivating the genome within,
resetting its developmental instructions to a pristine state. Once that happens,
the rejuvenated cell can develop into a full-fledged animal, genetically
identical to its parent. For agriculture, in which purely
physical characteristics like milk production in a cow or low fat in a hog have
real market value, biological carbon copies could become routine within a few
years. This past year scientists have done for mice and cows what Ian Wilmot did
for Dolly, and other creatures are bound to join the cloned menagerie in the
coming year. Human cloning, on the other hand, may be
technically feasible but legally and emotionally more difficult. Still, one day
it will happen. The ability to reset body cells to a pristine, undeveloped state
could give doctors exactly the same advantages they would get from stem cells:
the potential to make healthy body tissues of all sorts, and thus to cure
disease. That could prove to be a true "miracle cure."
单选题
The author believes in the passage that ______.
A. there will inevitably be human cloning in the coming year
B. the potential to make healthy body tissues is undoubtedly a boon to human
beings
C. it is illegal to clone any kind of creatures in the world
D. it is legal to clone any kind of creatures in the world except
human