Monday, December 17, 2012

A Suspect with Two Different Kinds of DNA

Can a character have one kind of DNA in his semen and another in his blood?

Yes—and it doesn’t require fantasy or magic. You’re describing a genetic chimera.
What is a chimera? In Greek mythology, this was a fire-breathing creature with the body of a lion, a goat’s head growing out of its back, and a tail comprised of a serpent.
Human chimeras are individuals with two distinct populations of cells. This can occur several different ways, but the most common is this:
Two separately fertilized ova start off as fraternal twins. Very early on, the two embryos fuse into a single individual, and the two sets of DNA are contained within that single individual. If chromosome set #1 produces the testicles and chromosome set #2 produces the blood or is responsible for the mucus membranes of the mouth (where a cheek swab for DNA is done), the two genetic profiles won’t match.
Chimeras occur more frequently in cases of in vitro fertilization.
Placental transfer of cells between mother and fetus can result in microchimerism—very small populations of genetically different cells in the mother or the fetus or both. The presence of fetal cells in the mother may have some connection to autoimmune disease (conditions in which the body perceives some of its own cells as foreign and attacks them).
Blood transfusion has been connected to microchimerism as well.
Most chimeras go through life without being discovered. The most popularized cases have been related to genetic matching for organ transplant and child custody.

Questions? Comments?
~*~
Kelly has worked in the medical field for over twenty years, mainly at large medical centers. With experience in a variety of settings, chances are Kelly may have seen it.

Sometimes truth seems stranger than fiction in medicine, but accurate medicine in fiction is fabulous.
Find her fiction at www.kellywhitley.com.
Book blog: www.kellywhitleybooks.blogspot.com

22 comments:

  1. My understanding (and I could be wrong) is that this also could happen if you have had a bone marrow transplant. If that happens, then your bones are making blood with one set of DNA and the rest of your bodily fluids like saliva and semen are still working with your original blueprints and churning out your own.

    These always interest me, Kelly. I do not write medical fiction, but I work in a medical-related field and they always tickle my fancy.

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  2. You're right.
    The blood is one type, the tissue is another--unless an identical twin donated the marrow! :~D
    Glad you're enjoying the posts!
    Cheers, Kelly

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  3. wow, that is so interesting. Not just from a writers approach but everyday knowledge. Great post.

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    1. Thanks, Cassandra.
      It is cool, isn't it?
      Cheers, Kelly

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  4. That was really interesting! Thank you for sharing!

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    1. Very welcome, Samantha.
      I love writing up these tidbits!
      Cheers, Kelly

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  5. Very intersting. I saw a documentary on this on the Discovery Health Channel. Thanks for sharing.

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    1. It is cool, isn't it?
      Would make for an excellent who dun it!
      Cheers, Kelly

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  6. Another way for the sperm DNA to be different than the blood DNA is for the person to be a genetic mosaic. They could be missing a Y chromosome in the blood karyotype but not in the sperm. Or they might have trisomy 21 (Down's) in the sperm but not in the blood (or vice versa).

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  7. This is very interesting. And something I did not know.

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    1. Glad I could show you something new!
      Cheers, Kelly

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  8. This is so very interesting, Kelly! Thank you for posting this.

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  9. Something else I didn't know! Enjoying your blog!

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  10. Great info, Kelly, my mind is already creating scenes for this. :)

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    1. The imagination does run wild, doesn't it?
      :~D

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  11. Lots of comments about bone marrow transplants.
    Yes, those folks have two kinds of DNA; the catch is they know they're chimeras and it's easy to track down. The major tissue matching proteins (HLA complex)will be close, because a bone marrow transplant needs to be compatible.

    The kicker about natural chimeras: their HLA complexes can be a complete no match.
    In addition, they rarely know they are chimeras--unless a need for genetic testing arises: paternity/maternity, organ transplant, etc.
    You or I could be a chimera--without testing, we'll never know. :~D
    Cheers, Kelly

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  12. Your blog is a most interesting and informative one. I have heard about people with two DNAs but didn't know how that happened. Now I do. Great blog.

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