Re: AGING: Accumulation of DNA damage

Date: Mon Jun 26 2000 - 12:56:56 MDT

Robert write:
> As I've stated for may years (since my comments in the early
> '90's on and bionet.molbio.ageing),
> DNA damage accumulation *should* be part of aging.
> I base this entirely on the observation that mutations
> are known to accumulate and in single cells that get
> amplified lead to cancer.

By itself this observation doesn't seem to establish your conclusion.
The fact that DNA is damaged, and damage accumulates, doesn't imply
that it is a cause of the phenomenon that we call aging. It could
be that aging is caused by something else, and that while DNA damage
would eventually lead to death, the symptoms and the time scale would
be completely different from what we think of as aging. Maybe you'd
live 1000 years and then your cells would all turn to cancers.

There may be other reasons to believe that DNA damage is a cause of aging,
but the mere fact that damage accumulates over time isn't enough.

> Now, so long as the cloning is done in a way to remove the brains,
> I think the ethical issues are specious, but this *does* raise the
> point that you may have to do 30 clones to get one good one
> (if you are interested in whole body transplants).

As we've discussed before, intentionally producing brainless humans is
not going to be considered by most people as a way to resolve ethical
issues. Rather, it raises a host of questions of its own. Start off
with Huxley's Brave New World and discuss whether that system, which has
some similarities to this idea, is moral. In particular, the epsilons
are produced by poisoning their brains during development so they are
nearly mindless, drooling automatons. It's not a very attractive image.

> It does however in my mind provide a significant amount of gravity
> for the DNA Damage theory as being a factor in the aging process.
> The developmental genes in an adult can accumulate mutations and
> you will never know it. But if you try to grow a new adult using
> those genes with accumulated mutations, then the results detailed
> above are a likely result.

Is it reasonable that as many as one cell in 30 has escaped harmful
DNA mutations, so that it is in good enough shape to create a whole new
organism from scratch? These are ordinary cells that have been dividing
and growing and metabolizing for a substantial fraction of the lifespan of
the animal. If DNA damage is the limiting factor, I would have expected
ordinary tissue cells to be more than 30 times worse than the egg cells
(which presumably have extra protection against damage).


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