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One of the greatest introduction to the scientific world
in recent times must surely be the introduction of
Dolly, a sheep in Britain. Dolly is no ordinary sheep.
It is an exact replicate, genetically of another adult
sheep. The successful cloning of Dolly has captured the
imagination of a worldwide community. Its implications
are simply mind-boggling.
Prior to Dolly's birth, scientists once thought that the
biological development of cells was irreversible. As an
organism grows, its cells divide. Then, the cells become
more specialized by switching on certain genes inside
their nuclei and shutting down others. People assumed
that the genes were shut down for good, but Dolly's
arrival appears to show that the process was
reversible. To make Dolly,
Ian Wilmut and his colleagues had to wind back the
development of an adult cell. The cell was biochemically
reprogrammed to begin life all over again.
Pioneering experiments had begun as early as in 1970,
when a team led by John Gurdon at the University of
Cambridge transplanted nuclei from the skin cells of
adult frogs into frog eggs lacking their own nuclei.
While some grew into tadpoles, none reached adulthood.
Wilmut says the key to his success lies in the unique
way his team manipulates the cells.
Now that an adult sheep has been cloned, there
appears no reason why we could not do the same with
humans. Scientists can select a cell from a human donor,
fuse it with an unfertilized egg and implant it into a
surrogate mother's womb. However, we are not there yet.
Working out the biochemistry and limits of this
`reprogramming of cells' will keep the researchers busy
for years. Nobody knows for sure whether clones could be
made with any human adult cell. "Brain and muscle cells
are probably so specialized that you can't reset their
clocks," says Wilmut.
The idea itself is truly amazing and it is not
impossible. However, some people feel a kind of horror
about producing clones. In Britain, there is already a
law against human cloning. In the States, the government
is reviewing the implications of the breakthrough.
President Clinton has said, "I believe we must respect
this profound gift (human life) and resist the
temptation to replicate ourselves." If human cloning is
possible, these are the ethical questions that need to
be considered. `Who would assume responsibility for her
welfare? Who would be her parents and how would she cope
psychologically and socially?'
On the other hand, there are also interesting
possibilities. "In many ways cloning could offer
enormous benefits," says one scientist. "You could clone
from an adult or a child who is sick to produce cells
that can be used to repair the individual's damaged
tissues." Potentially, scientists could even create
brain-dead copies of humans as sources of
perfectly-matched organs transplants. Even then there
are objections to this. If brain-dead clones were
nurtured and used as organ banks, "This would radically
change the nature of what it is like to be human."
The breakthrough that Dolly has achieved has been
described as 'one giant leap into the unknown'. "Most of
the things this technique will be used for have not yet
been imagined," says Wilmut. Nevertheless, with all the
heated debate that it has generated, it seems apparent
that mankind is not ready to face a real living human
clone yet. |
