Pocket Doc
Issue date: 3/8/10 Section: Pulse
|
Q. How does Chimerism work?
A. Just imagine how it would upset TV crime shows and soap operas if DNA evidence for crimes and paternity suits no longer had validity. For decades we've had it drummed into us that our DNA is our "unique fingerprint". Unless, of course, we are chimeras in which case we may have 2 different fingerprints!
Chimeras are genetic oddities that have formed embryologically by the fusion of 2 separate fertilized ovums at an early stage. With further development, the organism has 2 different cell lines and hence 2 different DNAs. One of the first cases to come to light involved a mother who was proven by DNA to have not borne her own children! Later testing revealed a second line of DNA in her cervical tissue that matched her kids.
Other mechanisms for chimeras are thought to be the fetal transfusion of small amounts of blood between fraternal twins with one twin dying at an early stage. The surviving twin retains some of the second line of DNA in its bone marrow and resultant blood cells.
The most bizarre presentation of chimerism is when the 2 early fertilized ovums are of opposite sex. Further development may have various outcomes including both ovaries and testicles, ovary on one side, testicle on the other, and so forth. As far as I know, no one individual possesses the necessary anatomic requirements to fulfill the common epitaph we've all heard many times. (No, I won't spell it out)
One more interesting consideration. Since your immune system is introduced to both cell lines at a very early stage, there is tolerance and not rejection to both lines. Being a chimera, therefore, should double your pool of possible donors for organ transplantation.
Send your anonymous questions to pulse@chicagoflame.com.
Be the first to comment on this story