[Aracelis]

Thanks for the ping, Junior. As I said, if it's science, religion or politics, ping away...I'm simply not interested by the endless crevo debate.

An article you may find interesting on the subject of chimeras:

Human Genetics: Dual Identities

What troubles you about this condition? Is it that most of these individuals seem to be the product of IVF, and thus there are some rather snarly metaphysical questions attached?

[Junior]

No. It's more that I'm a strong believer in the ensoulment of the individual at conception ("I knew you in the womb..." and all that). At conception, this woman was two different people which a short while later combined to form a single woman. Neither one of the individuals "died" in the process and each can be said to be living even now.

Does she have two souls? Did one of the twins actually die during the melding process and the woman could be considered as having a massive organ transplant?

I dunno, this "chimera" concept bothers me a whole lot more than I thought it would. I would never let personal beliefs deny the existence of evidence (unlike some folks I've seen on this forum), but that doesn't mean I don't try to reconcile the two.

[Ichneumon]

I was about to mention mosaicism as a variation of chimerism, but then I saw that your linked article had a good overview of it.

Quick teaser: Mosaicism occurs when one of the cells in the early stages of the embryo suffers a copy error or other type of mutation during cell division, ultimately resulting in an individual who has some parts of his body (those composed of cells "descended" from the faulty cell) genetically different from the other parts of his body.

I first found out about this syndrome while researching possible causes for my wife's atypical migraines. Mosaicism can cause all sorts of bizarre medical cases, since the symptoms (if any) depend upon the vast numbers of ways that cells can "fumble" their DNA, multiplied by the vast numbers of ways that the good cells / bad cells can be distributed in the body (causing only certain tissues/organs to be affected, and not others).

As PW's linked article mentions, research is underway to see if mosaicism might be responsible for some cases of autism and alzheimer's, for example.

[MHGinTN]

Several IVF clinics are now needle injecting a single sperm into the harvested ova, instead of exposing the ova to massive amounts of sperm in the dish.