Hey it’s Mike Chen, let me ask you guys, have you ever wanted a brother or sister?
Maybe more specifically, have you ever wanted a twin brother or sister?
I personally never really did mainly because I hate sharing stuff and when I was growing
up, we weren't the most wealthy family, and the thought of having to share the studio
apartment I already shared with my parents was really not the most appealing but then
again it would have been kinda nice to have someone to grow up with and maybe support
you through all the awkward Asian family mealtimes and vacations I had to go through... pretty
big revelation about myself (if you're interested) at the end of this video...
Anyway, so in this video, of course, we are going to talk about twins but did you know
that sometimes a twin pregnancy does not always yield twins.
Because sometimes one twin is absorbed or fused to the other resulting in one baby and
this is the case with the talented singer, Taylor Muhl.
Taylor always wondered what appeared to be a large birthmark on the left side of her
torso.
When she visited her doctor to find out about the different pigmentation on her torso, she
was shocked to find out that what looked like a birthmark is actually her fraternal twin!
Further tests revealed that her twin has her own DNA and separate genetic code.
Taylor admits to feeling relieved that finally, things made sense because one side of her
body always felt kinda different.
Her organs were slightly larger on the left side.
She also experienced various aversion to foods, jewelry, medications and insect bites on just
the left side of her body.
So what exactly is chimerism?
Chimerism is a condition that occurs when at least 4 parent cells are fused to form
one fetus.
By four parent cells, I mean two separate eggs fertilized by two separate sperms to
create two different embryos.
These embryos have distinct genetic characters and DNA.
When these embryos combine to form the same fetus, each zygote maintains its own genetic
code.
Chimerism occurs in both animals and plants and there are two types of chimerism in animals
namely; tetragametic chimerism and microchimerism.
Tetragametic chimerism occurs when two genetically independent cells combine into one fetus,
like in the case of Taylor Muhl.
Each classification of DNA possesses its own character traits.
Tetragametic chimeras can go their whole life without ever knowing.
Some of them, however, have distinguishing characteristics.
The most common signs include different colored eyes (heterochromia), uneven pigmentation,
ambiguous genitalia, different blood groups and immunity systems, and disparity in organ
sizes.
This all depends on the distribution of DNA of the two different entities throughout the
body.
If one DNA is dominant, most of the body organs will match that DNA leaving a few areas for
the docile DNA.
Now the thing is, identical twins can intermingle into the same baby but they are not exactly
considered chimeras.
This is because the genetic composition of identical twins is very similar.
Microchimerism is caused by either a medical procedure or as an inherited trait.
That's right, medically induced microchimerism can occur as a result of blood transfusion
or bone marrow transplant.
After a blood transfusion, the DNA of the donor body remains alive in the recipient
for 115 days.
In the case of bone marrow transplant, the DNA of the donor remains in the body of the
recipient forever.
After Taylor Muhl was diagnosed with chimerism in 2009, there has been an increased awareness
of the condition.
As it turns out, chimerism is not really uncommon.
For example, in 2002, Karen Keegan needed a kidney transplant.
Things got complicated when DNA testing to find a suitable donor revealed that she couldn’t
be the mother of two of her three children.
Later it was proven that she was a chimera and the DNA in her blood cells didn’t match
her organs.
Later that year, Lydia Fairchild almost lost custody of her children when DNA results indicated
they could not be her children.
Luckily her lawyer launched a defense based on Karen Keegan’s case proving that Lydia
Fairchild was a chimera and the only DNA matching her children was from her cervix.
And this is all really relevant because as we find out more about chimerism, there is
no denying the impact it is going to have on how we view genes and DNA.
Because if you consider the current role DNA plays in our identification processes, DNA
evidence can single-handedly incriminate or exonerate a person.
Rare as it may be, we cannot ignore the impact chimerism has on our theory of one person
equals one DNA.
Because, now it is possible that multiple people can possess the same DNA and vice versa.
And this is going to impact a lot of fields, including criminal justice.
Comprehensive DNA testing comprehensive DNA testing now has to include samples of bone,
hair, saliva, semen, and skin tissue.
Not just to eliminate the chances of tetragametic chimerism but the more common microchimerism
as well.
Ultimately, the reality of chimerism is little known and somewhat scary, because you have
two people in one person.
But it is also another one of life’s mysteries and wonders.
Anyway, so what I was alluding to in the beginning and I wanted to talk about at the end, and
why I wanted to do this video is because this condition also applies to me as well.
I never really talked about this in any one of my videos, I think maybe I mentioned it
a couple times during a discussion once, but I had a twin brother.
I had a twin brother who was with me in my mother's womb and unfortunately he did not
survive.
But the doctors said that I actually absorbed a lot of him in me.
Maybe this is why I always talk to myself, I'm not sure.
And this is not like some multi-personality, split personality disorder or anything, I'm
not crazy, but sometimes I feel like there's like two people in me, I don't know how to
explain it.
Anyway, I thought this was a really interesting topic to do a video about, hopefully you guys
enjoyed it.
Thank you all so much for watching, I'll see you later.