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  1. #1
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    mtDNA- Mitochondrial DNA -questions

    Mods feel free to merge if there's a thread on this already, i couldn't find one. I thought maybe some of us could use a little crash course on mtDNA.
    I understand that it is passed down through the females. What I am unclear on, is if it is the only type DNA test they are able to do, on these hairs, and if so, why? Is it because the paternity is unknown? But JG had a paternity test done that included Caylee's DNA, woudln't that be of some use?

    Thanks in advance for any answers from those who understand the subject better than I do.

    Is there a reason they are not testing for nuclear DNA?
    http://www.fbi.gov/hq/lab/fsc/backis...1999/dnaf1.htm

  2. #2
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    Great idea for a thread!

  3. #3
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    From what I understand from web research, mtDNA can be collected from the hair itself and doesn't require the follicle. It looks like much the same can be done with fingernails.

    I've seen reports of mtDNA used in cases with badly degraded, or small samples of DNA from things like teeth and bones. Since the advent of PCR amplification where very small samples of nuclear DNA can still yield results, I'd guess they use mtDNA less and less.
    Last edited by Where's Andre; 10-25-2008 at 12:14 PM. Reason: typo

  4. #4
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    I understood from the report (so far!) that there were no specimens in which nuclear DNA could be found. Just the hair sample without the follicle, so mtDNA only.

  5. #5
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    The Hair

    Quote Originally Posted by Capri View Post
    Mods feel free to merge if there's a thread on this already, i couldn't find one. I thought maybe some of us could use a little crash course on mtDNA.
    I understand that it is passed down through the females. What I am unclear on, is if it is the only type DNA test they are able to do, on these hairs, and if so, why? Is it because the paternity is unknown? But JG had a paternity test done that included Caylee's DNA, woudln't that be of some use?

    Thanks in advance for any answers from those who understand the subject better than I do.

    Is there a reason they are not testing for nuclear DNA?
    http://www.fbi.gov/hq/lab/fsc/backis...1999/dnaf1.htm
    The root of the one hair that was a match to KC or Caylee was not available & that root would have yielded the DNA proper or nuclear. It does not have to do with Caylee's unknown paternity and that line is not involved in mitochondrial DNA. The one hair did have a death ring or death band (same) and so it was not KC's or Cindy's or great grandmother's. It was Caylee's by all statistical probabilty determined by frequency in the population.
    Last edited by Tuba; 10-25-2008 at 12:21 PM. Reason: remove plural

  6. #6
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    Excerpt from an article explaining mtDNA:

    http://www.talkorigins.org/faqs/homs/mtDNA.html
    Mitochondria (singular: mitochondrion) are small energy-producing organelles found in cells. Surprisingly, mitochondria have their own DNA molecules, entirely separate from our nuclear DNA. Most cells contain between 500 and 1000 copies of the mtDNA molecule, which makes it a lot easier to find and extract than nuclear DNA. In humans the mtDNA genome consists of about 16,000 base pairs (far shorter than our nuclear DNA), and has been completely sequenced (for one individual, at least; Anderson et al. 1981). What makes mtDNA particularly interesting is that, unlike nuclear DNA which is equally inherited from both father and mother, mtDNA is inherited only from the mother, because all our mitochondria are descended from those in our mother's egg cell (there may be exceptions to this rule, however; see below).

    Link to more forensic mtDNA info:
    http://www.orchidcellmark.com/forens...mtdnaanalysis/

  7. #7
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    Quote Originally Posted by Tuba View Post
    The root of the one hair that was a match to KC or Caylee was not available & that root would have yielded the DNA proper or nuclear. It does not have to do with Caylee's unknown paternity and that line is not involved in mitochondrial DNA. The one hair did have a death ring or death band (same) and so it was not KC's or Cindy's or great grandmother's. It was Caylee's by all statistical probabilty determined by frequency in the population.
    I think this may be the evidence Baez was concerned about being destroyed. Nuclear DNA testing requires destruction of the hair.

    Sorry, responded to wrong post. ETA: this may be why they didn't attempt a nuclear DNA profile?
    Last edited by treeseeker; 10-25-2008 at 12:33 PM. Reason: clarified post

  8. #8
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    Mitochondrial dna is not passed down through females. It is passed from mother to offspring, be it male or female. Lee has the same mitochondrial dna as Cindy and, I would assume, Casey and Caylee. Casey can pass her Mtdna to her children but Lee cannot.
    Mtdna can withstand heat better than nuclear dna, the latter degrades very quickly in a hot environment (hours to just a few days). I believe this is why Mtdna is all that will be extracted from that trunk considering how hot it would have been in there and how long any nuclear dna would be exposed to the heat.


  9. #9
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    mtDNA is also more numerous (100-10,000 per cell) and simpler than nuclear DNA (16,500 base pairs v.s. 3 billion).

  10. #10
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    Quote Originally Posted by lizzysf View Post
    I understood from the report (so far!) that there were no specimens in which nuclear DNA could be found. Just the hair sample without the follicle, so mtDNA only.
    So, nuclear DNA is not in the hair itself, only the follicle?

    Just trying to understand all this. My thinking would be if they had nuclear DNA reasults, it could directly identify the exact person.

    Not just any offspring from KC (which would include any miscarriage). I do not believe KC had a miscarriage, only that I wouldn't put it past the defense to use something like that.


  11. #11
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    Quote Originally Posted by Capri View Post
    So, nuclear DNA is not in the hair itself, only the follicle?
    That's correct, from what I understand. The hair itself does not contain nuclear DNA. Hair is comprised primarily of the protein keratin and, except for the root, is not actually living tissue.

    http://www.opendemocracy.net/arts-hair/article_721.jsp

  12. #12
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    Quote Originally Posted by TXredhead178 View Post
    That's correct, from what I understand. The hair itself does not contain nuclear DNA. Hair is comprised primarily of the protein keratin and, except for the root, is not actually living tissue.

    http://www.opendemocracy.net/arts-hair/article_721.jsp
    thanks, interesting article too. So, they had to have the root bulb for the nuclear DNA.

  13. #13
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    DNA -- Important or not?

    My first thread on this board. Can someone explain to me why DNA is not important in this case? I would like to know more about the hair banding, which my husband and I have debated profusely for days. I would also like to know who Caylee's father is. It is important information we need to know.

  14. #14
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    I have always wondered why it's so important for people to know who is Caylee's biological father. I'm not being snarky, I'm just curious. Would it have any bearing on this case or what KC did to Caylee? I think it's a shame that whoever he is he was cheated out of a relationship with his daughter and she was cheated out of a father. But at this point, it just doesn't matter much (at least that I can see). And yes, DNA matters in the evidence in this case and I don't think there are any gorillas in the room. There's tons of evidence that has not been released, you can be assured of that.

  15. #15
    Quote Originally Posted by dunlurken View Post
    My first thread on this board. Can someone explain to me why DNA is not important in this case? I would like to know more about the hair banding, which my husband and I have debated profusely for days. I would also like to know who Caylee's father is. It is important information we need to know.

    I haven't read or been able to think of any reason why the identity of Caylee's father is important to this case. (Personally I'm not even curious about it either, having chalked it up to one of many possibilities due to promiscuity.)

    I'm always open to learning though and being enlightened certainly. Why do you feel it's important we know who the dad is, dunlurken?

    I do think DNA is important for narrowing down who the hair with banding belongs to. My understanding is that it's been narrowed to Casey or Caylee. Casey can be proven in the courtroom to be alive. Therefore the hair with banding can only come from Caylee.

    I had to be away from WS unexpectedly for a few days, and have completely caught up yet, so I could have missed something.

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