From: Robert J. Bradbury (bradbury@aeiveos.com)
Date: Tue May 28 2002 - 00:48:46 MDT
On Tue, 28 May 2002, Damien Broderick, commenting on my comment about
the data for natural conception failures, wrote:
> No it doesn't, not if cloning succeeds in, say, less than 0.5% of attempts
> (but maybe the success rate has gone up lately?). A Roslin site (
> http://www.roslin.ac.uk/public/cloning.html ) says:
>
> >Success rates remain low in all species, with published data showing
> >that on average only about 1% of 'reconstructed embryos' leading to
> >live births. With unsuccessful attempts at cloning unlikely to be
> >published, the actual success rate will be substantially lower
Ok, 27% / 0.5% = 54. So cloning is 54x (less than 2 orders of magnitude)
worse than natural conception. Given the fact that you are doing something
that the cells involved didn't evolve to do, I can accept that hit as
being "reasonable". In contrast to the development processes for eggs
and sperm where one would expect there to be a priority on the preservation
of genomic integrity, the cells being used as sources for genetic material
in nuclear transfer do not have much selective pressure on them to do
that (in adults the evolutionary bias for cells with really messed up
genomes is to undergo apoptosis).
Now, where it will get interesting is if turns out that the success
rate goes up as one selects cells closer and closer to totipotent
stem cells. Then one will be able to explain the failure rate in
terms of (a) accumulated genomic damage; and (b) decreased amount
of genomic reprogramming that has to be done (using quasi-stem
cell nuclei).
Robert
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