Chimera in Humans
Country: United States
Date: May 2007
I would like to know if it were at all possible to
create a human/animal chimera?
Early embryos can fuse to develop into a single organism. If this
happens, the resulting organism, known as a chimera, will have some cells
from one embryo and some cells from the other embryo. The most famous
example of this is the "geep" which is the resulting organism from the
fusion of goat and sheep embryos and has regions on its skin with sheep wool
and regions with goat hair. In humans, there have been cases where fetuses
that would have normally developed into fraternal twins fuse to form one
fetus, and in these cases the humans will be chimeras in that they have
cells derived from two separate zygotes (fertilized egg cells).
While there are moral concerns with trying to create a human/animal chimera,
a lab from University of Nevada, Reno actually created chimeric sheep with
15% human cells in the hopes of creating animals whose organs could be used
for transplantation into humans. They did this by injecting human cells
into developing sheep fetuses, and while the animals produced looked like a
normal sheep, their organs contained human cells. While this is a far cry
from a talking half-human sheep, these animals are human-animal chimeras.
Stanford Department of Chemistry
The case of the woman who is her own twin (Aired on Discovery Health) shows
that she is apparently the result of the fusion of two fertilized eggs, one
destined to be a female and the other a male (her fraternal twin brother).
Many of the tissues in her body (blood, ovaries and cheek cells) carried the
DNA of what would have been her fraternal twin brother. They eventually found
"her" DNA in her thyroid cells which matched the DNA of her children. So
chimeras apparently do ocur during embryonic development.
Ron Baker, Ph.D.
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Update: June 2012