From: Ramez Naam (mez@apexnano.com)
Date: Fri Nov 29 2002 - 23:25:32 MST
From: Robert J. Bradbury [mailto:bradbury@aeiveos.com]
> > The genes we have, in many cases, have their most profound
> > effect on us during our developmental phases - as embryos,
> > newborns, children, adolescents, etc... The later in
> > life you intervene, the less of an impact you will have.
>
> Why? Cannot lizards regrow their tails, lobsters claws,
> etc.? The flexibility for significant self-modification can
> be programmed into the genome.
Unless, of course, those regenerative abilities you mention required a
great deal of infrastructure that is laid down during lizard or
lobster development. (I honestly don't know.)
>
> > In an earlier version of this thread I used the example of
> > homeobox genes in the fruit fly. We can manipulate these
> > in an embryo and in so doing give the adult fruit fly an
> > extra pair of wings or legs or whatever.
>
> But the examples I cite above seem to suggest there is no
> reason one couldn't do these things in adult organisms. A
> good example that could be done with "current" technology
> would be a bone marrow transplant of ones own stem cells with
> the CCR5 gene knocked out. Voila -- you have your own immune
> system back with a significantly higher resistance to HIV.
I think it depends on how complex the change is. If you're talking
about a change to the expression of one or a few proteins, I have no
problem believing that you can do this with gene therapy.
If you're talking about a change to gross morphology (adding new limbs
or organs) or to cognitive architecture (significantly rewiring the
brain), then I think you're in a much more complex space.
In humans, morphology and cognitive architecture are laid down during
early development, both as an embryo and in critical years after being
born. We simply don't grow new limbs or new brain regions
spontaneously after a certain age as embryos.
Let's say you wanted to make an adult human grow a new mental capacity
- the ability for 4D visualization, say, or a new mental organ that
could do fast mathematical calculation. To make this a reality, you
would have to cause a cascade of events that involved the genesis of
new neurons, the release of neural growth factors, the formation and
pruning of hundreds of millions of synapses, the vascularization of
those areas, the *physical expansion of the brain and skull* to
accommodate that area, the innervation of all related areas by these
neurons, etc...
I think this would be a huge huge problem. First of all, just
figuring out how to do this by inserting genes seems more challenging
than anything mankind has ever done. Secondly, doing this in a way
that preserves the basic integrity of the organism's personality,
memories, etc.. (let alone not just outright killing the subject)
seems even more challenging.
> > However, if you were to try making this same genetic change
> > to an adult fruit fly, I predict you would get a result far
> > different (and probably far more lethal) than you get by
> > making the change in an embryo.
>
> Predict based on what?
I predict this based upon my layman's knowledge of genetics and
biology, of course. :)
> There is nothing to suggest that genomes cannot
> be programmed for significant changes (tadpole to frog,
> catapillar to butterfly, etc.)
These are good examples. But again I have to ask: is there
significant infrastructure for these transformations already laid
during the developmental process of the earlier phase? Once again I
plead ignorance, though I have my suspicions.
> Yes, but I don't believe you saw my talks at Extro-3 or
> Extro-4 and you haven't read my current business plan. [several
:-)]
Well then, shoot me copies of any or all of the above and maybe you'll
change my mind. :)
stimulated, as ever,
mez
This archive was generated by hypermail 2.1.5 : Wed Jan 15 2003 - 17:58:30 MST