http://www.academicpress.com/inscight/10061999/graphb.htm
This article mentions that "because after conception only the egg's
mitochondria survive, mtDNA forms a continuous thread running back
through time through the maternal lineage." This is not strictly true.
It has been demonstrated that some mtDNA can enter the egg with the
sperm. But.....
I quoted this particular sentence because of a recent post by Glenn
regarding two studies published in the Proceeding of the National
Academy of Science. This research seemed to indicate that there might
be some paternal contribution to the mtDNA lineage. These studies are
very equivocal. There has been at least one response in Science
disputing these reports. I do not have the reference at my fingertip,
but I have a copy of the article here on my desk somewhere (buried under
textbooks and homework.)
In addition, I have also been in contact with an acquaintance, a
biochemist and microbiologist who is doing research in the mitochondrial
DNA. He has told me about an incredible biochemical system which seems
to specifically target paternal mtDNA and destroys it within the first
few cleavages of the egg. It seems there is a group of biochemists who
get all excited when talking about something called Ubiquitin-Mediated
Targeted Protein Degradation. Apparently this is a hot new area of
research. (I hope the biologists on the list will help me out here if I
am too off base.)
It seems that by time the paternal mtDNA has entered the egg it is so
badly degraded that its presence would be very harmful to the developing
embryo. This process (Ubiquitinylation) is supposed to seek out and
destroy this mtDNA. There are supposed to be some reports coming out
soon about this soon. There was also a "popular" article in Scientific
American about this recently. It can be viewed at :
http://www.sciam.com/1999/0399issue/0399scicit1.html
At any rate, the biologists I have talked to do not give great credence
to this report about paternal mtDNA.
Blaine McArthur