Re: mitochondrial DNA and Sperm RNA

["Judith Rosen" <***>]

That was a fascinating article, Tim. It was one I hadn't seen before. I
followed the trail from that one to a whole bunch of others and it seems
that sperm also carry several thousand "strands of paternal RNA" as well.
What I want to know is, where the hell do they put it?! Sperm travel light!

Another aspect to mitochondrial DNA that isn't often mentioned is that not
all the mitochondria in a single cell necessarily have identical DNA. I find
that amazing. I don't know under what circumstances this occurs or whether
it's "the norm" or an anomaly, but if you find any further information on
that, I'd be very interested.

One other comment worth passing along about results from various studies
that is often forgotten (but my father used to point it out all the time):
There are certain questions that need to be kept in mind when reading about
any given scientific study. In this case, those questions include: What
species of animal were the cells taken from? How does that species differ
from human beings? Under what conditions were the experiments conducted? In
other words, what context was this study conducted in? Because that can make
all the difference (ie: pregnancies weren't carried to term "in this
study"... what if the construction project next door to the laboratory was
upsetting the animals or something else unrelated to the conditions under
scrutiny that are not reflected in the documented material...)

That's not to say that this study was not useful, maybe it was truly
reflecting the nature of the thing being studied, but it's always good to
bear in mind that results of any single study need to be taken with some
room for doubt.

Judith

----- Original Message -----
From: "Tim Gwinn" <***>
To: <***>
Sent: Monday, December 15, 2003 11:34 PM
Subject: Re: [ROSEN] mitochondrial DNA


> Hi Judith,
>
> In my search tonite, I only found one paper online where they compared the
> efficacy of using maternal donor cells versus "foreign" donor cells (which
> would presumably have different mitochondrial DNA than from a maternal
cell)
> in cloning of cows. The paper notes that: "Consequences of constructing
> clones in a "foreign" egg cytoplasm remain unclear but may contribute to
the
> inefficiency of the cloning procedures for producing live, healthy
> offspring."
> The conclusion was: "Use of maternal egg cytoplasm for constructing cloned
> embryos did not improve developmental competence of clones to establish or
> maintain a pregnancy to term."
> I cannot tell what year the paper was written (at least 1998+). It is a
> short paper, from the Univ. of Tennessee, located at:
>
http://animalscience.ag.utk.edu/pdf/Reports/Edwards_LE%20departmental%20repo
> rt%20maternal%20cytoplasm%202002.pdf
>
>
> I also found the following item which states that sperm do have
mitochondria
> (they apparently do need them to produce energy) but these sperm
> mitochondria may be chemically tagged for destruction once inside an egg:
> http://www.findarticles.com/cf_dls/m1200/1_157/59021040/p1/article.jhtml
>
>
> It would seem to make sense that mismatches of nuclear and mitochondrial
DNA
> ought to promote problems, diseases and death among such clones. But, if
> this does not bear out, then perhaps the two are not that tightly coupled.
> That might offer some evidence that is suggestive of the notion that the
> mitochondrial components of cells were seperate organisms(?) at one point
in
> time, and at some later evolutionary time became endosymbiotes, and retain
> some degree of independence of internal structures from its symbiotic
> partner. As a symbiote, perhaps as long as the mitochondria serve their
> functional role for the whole cell, variations in their internal structure
> can be tolerated.
>
> Regards,
> Tim
>
>
> > -----Original Message-----
> > From: ROSEN Forum [mailto:*** Behalf Of Judith
> > Rosen
> > Sent: Monday, December 15, 2003 9:34 PM
> > To: ***
> > Subject: Re: mitochondrial DNA
> >
> >
> > Off and on over the years, I've done a bit of research into
mitochondrial
> > DNA, because I was fascinated with the notion that not all of our
"genetic
> > blueprint" is contained in the nuclear DNA. I also found it
> > interesting that
> > all mitochondrial DNA is inherited through the mother (because
> > the egg cell
> > is large enough to contain mitochondria but the sperm cell is not). This
> > doesn't get talked about very much, and I don't understand why that is.
It
> > seems to me that if certain inherited human metabolic diseases are being
> > studied, for example, then they ought to be looking into mitochondrial
> > DNA... but it has never gotten a single mention in any of the studies
I've
> > seen.
> >
> > With regards to Jeff's experiment idea, I think the mitochondria
> > must play a
> > large role in the genetic make up of any offspring resulting from an egg
> > where the mitochondria are not from the same mother as the nucleus. Does
> > anyone know of studies where this aspect of cloning is discussed? It
seems
> > to me that the premature aging that we've seen in cloned animals
> > may be due
> > to a mismatch in genetic proteins within cells or some other side-effect
> > from this situation.
> >
> > Judith
> >
> > ----- Original Message -----
> > From: "Jeff Pridaux" <***>
> > To: <***>
> > Sent: Monday, December 15, 2003 1:37 PM
> > Subject: Re: [ROSEN] SciAm Dec. 2003 - DNA, Epigenetics, and Complexity
> >
> >
> > > The following experiment might be interesting:
> > >
> > > As I understand it, for animals cloned so far, the DNA from a viable
egg
> > > cell is replaced with DNA from another cell (from the same
> > animal) in such
> > > a way to "trick" the egg to think it was fertilized.  It may be that
the
> > > whole nucleus is swapped out of the egg.  Then the animal (or a like
> > > animal) carries the fertilized egg to term resulting in a clone of the
> > > animal (who donated the DNA)
> > >
> > > An interesting alternative would be to have the donor egg and the
> > replacing
> > > DNA being from different animals.  And somehow just swap out the DNA
> > > without swapping out the surrounding chemicals around the DNA in the
> > > nucleus.  If that were possible and if an animal resulted that wasn't
> > > exactly the same as the DNA donor, then that would demonstrate that
the
> > DNA
> > > isn't EVERYTHING.
> > >
> > > I suspect, though, that this experiment may be very difficult (or
maybe
> > > impossible) to perform.
> > >
> > >
> > >
>
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