X-Message-Number: 7466
From:  (Steven Haywood)
Date: 09 Jan 97 02:58:00 -0800
Subject: Cloning

Reply-To: 


Subject: Cloning

In message #7338, Brian Wowk wrote the following:

>anywhere near as bad as hamburger), but the technology for
>turning hamburger back into cows has existed for years.  Furthermore,
>the technology for doing so is highly suggestive of the kind of future
>technology that might allow revival of cryonics patients.
>So (to prove that the average sci.cryonics reader is
>more imaginative than the average cryobiologist) can anyone guess
>how to turn hamburger back into a cow with existing technology?

In message #7341, Will Dye wrote the following:

>Well, I suppose you could mix the hamburger into the
>feed of another cow, and thus recycle many of the
>original atoms.  You could also produce (through
>various techniques) a cow that has much or most of
>the original cow's DNA, thus preserving an important
>pattern that was in the original cow's atoms.

    Few cells in animals are totipotent, past the early embryo stage.  In most
adult animals, even the most versatile cells are only pluripotent, which means
that although they can give rise to more than one kind of cell, they can give
rise only to a few kinds.  But most mammalian cells either do not divide at all
after a certain age or else can divide only to produce replicas of themselves.
    Although every nucleated cell of the body contains a copy of the entire
genome, only small clones of mammals can be produced--by splitting early
embryos.  Successful somatic cloning would require us to de-differentiate
already differentiated DNA.  One form of somatic cloning is already becoming
possible by culturing embryonic tissue, before the DNA is irrevocably switched
off.  Some agricultural research is already aiming to multiply "elite"
livestock in just this way.  Whatever can be done with cattle can almost
certainly be done with human beings.  The embryonic tissue route to human
cloning should, in short, be technically feasible within a few decades.


                                                                Steven Haywood


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