On Sun, 25 Mar 2001, Olga Bourlin wrote:
> What's up with this?
> (I know there are people on this list who will enlighten us ...)
I strongly suspect the problem is a lack of gene 'imprinting'.
Germ cell genes are imprinted by the mother and father in an
effort to cancel out each the "agenda" of the opposite sex.
I think one of the genes for which this occurs
is one of the "insulin-like-growth factors".
The male wants to promote the growth of large child so
it is born with a higher birth weight increasing its
chances of survival. The female wants to limit the
available resources that the baby can tap and also keep
the fetus from becoming so large that the mother dies
in childbirth. So the genetic program includes this process
of 'imprinting' (where the parent "label" the DNA as
being from the male or the female). This allows the
female to put constraints on the male genes that promote
excessive growth. There are probably other cases where
imprinting may occur that we don't understand yet.
If you use non-germ line cells as the source of the nuclei
you put into the egg, I suspect they will not have the
proper imprinting. I think when the science gets worked
out here its going to be pretty interesting. It isn't
a showstopper for cloning in the long term, but it may
slow it down a bit (probably a good thing).
Robert
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