twins

Tom Matthews tmatth at netcom.ca
Thu Feb 19 22:42:11 EST 1998


rEN wrote:

> In <34EBE78E.3066 at netcom.ca> Tom Matthews <tmatth at netcom.ca> writes:
 
> >Giuseppe Verdesca wrote:
> >>         Do the twin brother suffer from the same illness during their whole
> >> life but especially in age?
 
>     I've no idea about dieases in general, but it seems decline of
> cognitive ability may be under genetic influence (see: Science 276, p.1560,
> 6 June 1997)
>         That paper might be a good starting point for a literature
> search.
 
> <snip>
> >Even identical twins, however, are of at least two kinds. All share
> >original nuclear DNA, but some may have different mitochondrial DNA.
> <snip>
 
>       Forgive my ignorance, but pray tell how identical twins may
> possess different mitochondrial genomes?

This is not at all my area of expertise, so I should have phrased it as
a question instead of using a "may".

However, given that not all mitochondria in a given human cell have
identical DNA, given that ova have more the one mitochondrium, and given
that mitochondrial fission is not linked to mitosis, it would seem to me
to be possible that at the point of division of the original zygote
which produces the identical twins, the separated portions can contain
different amounts of the different mitochondria, perhaps even to the
point of one twin not containing any mitochondria with identical DNA to
that of the other. I know this can happen in other species.

If any more knowledgable readers can elucidate this, it would be
appreciated. 

--Tom 
Tom Matthews
 
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