implications of dolly
kkalafus at ABULAFIA.ST.HMC.EDU
Wed Mar 19 18:33:53 EST 1997
Certainly the cloning of Dolly has some interesting implications for aging
theory, but keep in mind:
1. The cell population used as the source of DNA in the cloning experiment
was mixed (not all the same cell type). According to the science paper in
which cloning was reported, the experimenters could not rule out the
possibility that Dolly arose from a stem cell -- if this is the case, the
cloning experiment does not tell us much about the reversibility of cellular
changes associated with aging because a stem cell would presumably be
protected from having undergone these changes in the first place.
2. Dolly's progenitor was only 6 years old when the cells were harvested.
A sheep can live to about 30 years. Even if the source of DNA was a normal,
terminally differentiated somatic cell, further information is needed before
we can conclude that a molecular clock was reset at the time of Dolly's
conception. It would be much more convincing if Dolly lived the maximum
sheep lifespan, or even better, if Dolly were herself cloned at some
Of course, the strength of evidence for reseting Dolly's molecular clock
largely depends on what sort of molecular clock you're talking about. The
ability of a terminally differentiated cell to replicate itself the
incredible number of times required to create an entire organism would argue
very convincingly that a clock which counts divisions has been reset.
Another thing to keep in mind is that the fusion of a normal cell with a
denucleated egg results in an embryo which has the mitochondrea from a
normal egg. This makes it impossible to rule out that aging has something
to do with damage to mitochondrea. Can anyone think of a way to permanently
inactivate the mitochondrea in the denucleated egg, without causing other
significant damage? Perhaps cyanide?
This definitely has the potential to tell us some interesting things about
the aging process. It would be unfortunate if the current negative public
opinions of cloning leads to a blanket ban on cloning research.
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