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Author Topic:   Mitochondrial mutation rate and the Romanov family
SAGREB
Inactive Member


Message 1 of 4 (316999)
06-02-2006 11:31 AM


Lately I was involved in a discussion with a creationist about genetic distances and times of divergences between different species, considering mitochondrial differences. I showed him that if dog and wolves diverged 5000 years ago, coyotes diverged a time at least 25000 years ago. These low ages was to give him something to compare with. He could not explain both the differences and times of divergence for these species, but he gave me a puzzling thing to think of. He mentioned that a faster mutation rate have been observed in a study of several generations of humans showing 10 different types of mitochondria. He also mentioned the tsar from the Romanov family having two kinds of mitochondria, either a C or a T at one position in the D-loop.
He gave me the links: http://www.mhrc.net/mitochondria.htm
and http://www.dnai.org/teacherguide/pdf/reference_romanovs.pdf
The following was part of the text in the last link. The most puzzling it mentioned was the results presented about the 357 induviduals from 134 families carrying 10 different types. Does this indeed show a faster rate or how could heteroplasmy be so extensive as 10 different types. What do you guys say about this? It was presented in "Nature Genetics 15: 363-368 (1997). The name of the article by Parson was "A high observed substitution rate in the human mitochondrial DNA control region"
The text from the last link here:
The researchers sequenced 610 base pairs of the mtDNA control region in 357 individuals from 134 different families, representing 327 generational events, or times that mothers passed on mtDNA to their offspring. Evolutionary studies led them to expect about one mutation in 600 generations (one every 12,000 years). So they were "stunned" to find 10 base-pair changes, which gave them a rate of 2 one mutation every 40 generations, or one every 800 years. The data were published last year in Nature Genetics, and the rate has held up as the number of families has doubled, Parsons told scientists who gathered at a recent international workshop* on the problem of mtDNA mutation rates.
Howell's team independently arrived at a similar conclusion after looking deep within the pedigree of one Australian family affected with Leber hereditary optic neuropathy, a disease caused by an mtDNA gene mutation. When the researchers analyzed mtDNA from 40 members of this family, they found that one individual carried two mutations in the control region (presumably unrelated to the disease, because it is noncoding mtDNA). That condition is known as triplasmy, because including the nonmutated sequence, he had three different mtDNA sequences in his cells. By tracing the mutations back through the family pedigree, Howell was able to estimate that both mutations probably arose in the same woman who was born in 1861, yielding an overall divergence rate of one mutation every 25 to 40 generations. "Both of our studies came to a remarkably similar conclusion," says Howell, whose study was published in late 1996 in the American Journal of Human Genetics. Both also warned that phylogenetic studies have "substantially underestimated the rate of mtDNA divergence."
Several teams of evolutionists promptly went back to their labs to count mtDNA mutations in families of known pedigree. So far, Stoneking's team has sequenced segments of the control region in closely related families on the Atlantic island of Tristan da Cunha, where pedigrees trace back to five female founders in the early 19th century. But neither that study nor one of 33 Swedish families has found a higher mutation rate. "After we read Howell's study, we looked in vain for mutations in our families," says geneticist Ulf Gyllensten of Uppsala University in Sweden, whose results are in press in Nature Genetics. More work is under way in Polynesia, Israel, and Europe.
Edited by Adminnemooseus, : Removed a bunch of extra line breaks. Also inserted some blank lines where it seemed to be new paragraphs.

Replies to this message:
 Message 3 by SAGREB, posted 06-08-2006 6:55 AM SAGREB has not replied
 Message 4 by Modulous, posted 06-08-2006 7:30 AM SAGREB has not replied

  
AdminNWR
Inactive Member


Message 2 of 4 (317003)
06-02-2006 12:00 PM


Thread moved here from the Proposed New Topics forum.

  
SAGREB
Inactive Member


Message 3 of 4 (318990)
06-08-2006 6:55 AM
Reply to: Message 1 by SAGREB
06-02-2006 11:31 AM


C’mon
What do you folks think about this?
Shall the creationists win this subject. 10 different mitochondria (10 different mutation variants) within 134 persons back to their original mother. Is this not a sign of a very fast mutation rate within the control region. I am not a creationist myself, but I don’t think we should ignore arguments that they actually can uphold.

This message is a reply to:
 Message 1 by SAGREB, posted 06-02-2006 11:31 AM SAGREB has not replied

  
Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 4 of 4 (318997)
06-08-2006 7:30 AM
Reply to: Message 1 by SAGREB
06-02-2006 11:31 AM


I've not seen this one before
And I don't think many others have either. I'm not wanting to commit to one line of reasoning before giving it due consideration. A quick look around would seem to indicate that there is some controversy surrounding the Romanov's samples...that is - it is unclear whether the mtDNA that was recovered actually came from the Romanovs, and that it was uncontaminated. I imagine that under normal circumstances the results obtained would be a falsification for the hypothesis that they are Romanovs rather than a falsification of the hypothesis of mutation rates.
As you indicate in the last part of the post - replication of these results with other reliable pedigrees has not happened.
Still, I'm keeping an open mind and waiting to see if any of the biologists have anything interesting to add.

This message is a reply to:
 Message 1 by SAGREB, posted 06-02-2006 11:31 AM SAGREB has not replied

  
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