How can a man who fathered a child also not be that child’s father?
Nope, there’s no secret funny business with the neighbour involved.
Just Chimerism.
Hey guys!
Amy with you on DNews today digging into the totally fascinating world of chimerism!
In Greek mythology, Chimera is a fire-breathing monster with the head of a lion, the body
of a goat, and the tail of a snake.
It is, in short, something that blends multiple species and thus can’t possibly exist in
reality.
Except that chimeras do exist.
Scientifically speaking, a chimera is someone with have multiple sets of DNA.
But if each individual has their unique DNA signature, then a chimera is… two people…
rolled into one?
Actually, that’s kind of what’s happening.
It happens when an embryo takes in its twin’s cells -- and therefore genetic material — in
utero.
Twins happen when a zygote splits.
But the moment of twinning — when the zygote splits — is actually really important because
the later zygote separation occurs, the more the two fetuses CAN share.
Two fetuses that don't entirely split can become conjoined twins, but ones dies, it’s
the same thing as losing a pregnancy early on but the remaining baby can be healthy.
It’s twin death in the first trimester that we’re interested in looking at.
When one twin dies, its material is sometimes absorbed into the surviving embryo causing
tetragametic chimerism.
This is more commonly known as Vanishing Twin Syndrome.
The surviving embryo will develop with both its and its twin’s DNA, meaning the child
will effectively be born its own twin.
This sounds nuts, but Vanishing Twin syndrome is way more common that you might think!
In 1945, Dr. Stoeckel was the first to suggest that the rate of multiple conceptions was
greater than multiple birth rates, that more zygotes divide than grow into fully formed
twins and the dead twin material is reabsorbed by the living twin without a trace — except
for the DNA trace.
Modern technology backs this with a rise in two placentas detected early on with ultrasound
and only one heartbeat heard later on with a sonogram.
It’s estimated that about one in every eight single childbirths start as multiple pregnancies
with cells from the miscarried sibling occasionally absorbed by the survivor.
Because our DNA is so fundamental to who we are, there are some really interesting implications
with chimerism.
Like proof of parentage.
Two women — Lydia Fairchild and Karen Keegan — didn't pass a maternity test.
They're not genetically the mothers of their own children even though they physically gave
birth to them!
The same thing can happen with fathers.
In 2015, a US man failed a paternity test, though he did seem to be his son’s uncle.
Doctor’s found that the DNA in his sperm was different than the DNA in his saliva.
His vanished twin had fathered his child.
Like maternity and paternity testing, the legal system relies heavily on DNA evidence.
In 2005, American cyclist Tyler Hamilton used tetragametic chimerism as a defense against
positive blood doping results, claiming the positive doping test was false because it
was actually his vanished twin’s blood.
And imagine if a chimera murdered someone.
DNA evidence on the scene could exonerate the perpetrator even if circumstantial evidence
offers definitive proof of their guilt!
Our DNA is pretty fascinating, and if you want to learn more about what makes us all
who we are, check out this video right here.
We’ll put a link in the description if you’re on mobile.
What you didn’t know about your dna
So this is all a little creepy, but really fascinating stuff!
What do you guys think about the possibility of being your own twin?
Let us know in the comments below and don’t forget to subscribe for more DNews every day
of the week.
So this is all a little creepy, but really fascinating stuff!
What do you guys think about the possibility of being your own twin?
Let us know in the comments below and keep coming back to Test Tube for more DNews every
single day of the week.
So this is all a little creepy, but really fascinating stuff!
What do you guys think about the possibility of being your own twin?
Let us know on the Discovery News Facebook page or on Twitter @DNews.
And you can find me; I’m @astvintagespace.
Thanks for watching!