Re: Babies with three parents?

Bob LeChevalier wrote:
> Steve Hayes <hayesmstw@[EMAIL PROTECTED]
> wrote:
>> If this goes any further, we may need genealogy software that allows
one to
>> enter three or more parents - and what would a pedigree chart look like
then?
>>
>> http://news.yahoo.com/s/ap/20080205/ap_on_sc/embryo_research
>>
>> LONDON - British scientists say they have created human embryos
containing DNA
>>from two women and a man in a procedure that researchers hope might be
used
>> one day to produce embryos free of inherited diseases.
>> ADVERTISEMENT
>>
>> Though the preliminary research has raised concerns about the
possibility of
>> genetically modified babies, the scientists say that the embryos are
still
>> only primarily the product of one man and one woman.
> 
> There might be four (or more).  There might have been a surrogate
> mother, and there is some evidence that genetic development is
> controlled in the womb in part by the maternal hormonal environment.
> The genes we are born with are not exactly the same as the ones in the
> fertilized egg, so that a surrogate mother is arguably part of one's
> genetic ancestry.

Strictly speaking, the DNA we are born with is precisely the set of 
chromosomes that were in the fertilised egg (23 from father, 23 from 
mother), plus the mitochondrial DNA, which comes from mother.

However, the expression of the genes in the DNA is controlled by a 
number of complex factors.  By "expression", I mean which genes are
active.

Biologists are still trying to understand how gene expression is 
controlled, particularly for those genes which we get in two copies, one 
from each parent.  In some cases, it's always the paternal copy which is 
active, and in others, it's always the maternal copy.

This book is a very good introduction to some of the issues involved:

http://www.amazon.com/X-***-Chromosome-Controls-Lives/dp/0674016211/

David Harper
Cambridge, England