From: Robert J. Bradbury (bradbury@aeiveos.com)
Date: Fri Mar 01 2002 - 10:03:19 MST
Actually I think Harvey misses one of the main problems with cloning.
The process doesn't get gene imprinting right. At least in
humans, the father seems to imprint the sperm to create a
large child at birth, while the mother imprints the egg
seeking the reverse. Presumably in the "common" case the
imprinting effects cancel each other out. This is an
exellent example of selfish genes at work. I believe that
imprinting is accomplished by special purpose enzymes that
methylate DNA in specific locations to alter levels of gene
expression.
The genes known to be imprinted include Insulin-Like-Growth-Factor-1,
I believe, so it isn't surprising that in cloned animals
could have problems with obesity. I don't know for sure
whether imprinting is the same in mice and humans though
and we have been caught by surprise before extending
conclusions in mice to humans (esp. in the telomere story).
So in addition to the telomere length problems, the
gene imprinting problems would argue against human
reproductive cloning.
Robert
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