Chimera Cats and Your Mom

Chimera Cats and Your Mom

[Theme Music] You know what’s fascinating and also a little bit gross when you think about it? Chimeras. Not the mythological ones but actual chimeras: organisms that contain the genetic information of more than one individual. And yes, this is a real thing. Chimeras are usually formed in the very early stages of embryonic development when two zygotes fuse into one and the resulting chimera basically ends up being its own fraternal twin. Which is. . . yeah. I know. And you end up with all sorts of weird conditions like if you’re a male and a female fraternal twin fuses into one sometimes you get one ovary and one testicle literally with different genetic information in them. There’s also this woman who needed a kidney and so they did a blood test on her kids to see if they’d be good donors, and they did it, and they were like “not only would they be bad donors but they aren’t your kids”. And she was like “Yeah, but, uh, they came out of me”. It turned out that her blood, and her organ systems, were from two different people. They had two different genetic makeups! So she gave birth to a different person than her blood would have . . . given birth to. And I’ll wager you a box of jujubes that you’ve heard of the adorable two-faced cat with mismatched eyes, Venus. She is often described as a chimera, but it turns out that she’s probably not. Instead, she appears to be what most female mammals are: a mosaic. See, a female has two X chomosomes one from her father and one from her mother. But as an embryo, each of her cells deactivates one of those two Xs at random so she ends up with two different groups of cells in her body: One with only her dad’s X and one with her mom’s. In humans this differentiation is difficult to detect because not a lot of traits are linked to those X chromosomes, but in cats, that distinctive tortoiseshell coloration that Venus has IS X-linked. So what we’re seeing is probably the arrangement of her different ‘mom X cells’ and ‘dad X cells’, that happen to line up down the middle of her very kissable face. So Venus may not really be a chimera, but try not to be too heartbroken, because you know who is? I’m sure you know one, actually, because you came out of one. Just today, scientists in Seattle say that they’ve found the first evidence of male DNA in the brains of women. After performing autopsies on the brains of 59 women, they found that two thirds of them contained different DNA and it was male: XY, not female: XX Now, the researchers don’t know the history of each woman whose brain was studied, but they suspect that the DNA got into their brains through whats known as ‘fetal chimerism’: when a pregnant woman receives cells from her embryo, which then go on to start lineages in the mother’s body that can last for the rest of her life. This phenomenon, also know as ‘microchimerism’, was first discovered in the 1990s in women’s blood, but this is the first time it’s been observed in their brains. This could change current thinking about how widespread chimerism is in women and also what implications it might have for the study of brain disorders like Alzheimer’s disease. So, as if those nine months weren’t enough, Mom, you’re still carrying a little bit of me with you wherever you go. Thanks for watching this episode of SciShow Breaking. If you want to keep up to date on the science news you can go to and subscribe. Questions, ideas and comments are always welcome on Facebook, Twitter and, of course, down in the comments below. [Theme music]

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  1. I carved my name in my moms uterus just before I was born…. I thought my name was buxinton at the time…. I was wrong… just saying.

  2. talk about put an end to abortions… those babies are really apart of you… sad to say might not be good to keep unatrually ripping parts of your body out of you.

  3. What if the pregnancy was not carried to full term? I only ask because many women have zygotes form that are not actually implanted and considered a "pregnancy" it happens all the time. Does that mean the X chromes could be linked to these? or only the bundles of joy that run around the house being messy. 

  4. So females can have male DNA in them. I have just my dad's DNA, but my two younger sisters were born after my little brother, who was stillborn, sadly, so they not only have our dad's DNA, but my little brothers DNA too? Wow, no wonder my sister's act crazy all the freaking time.

  5. So chimera is more or less, twin eating his twin.
    But what happens to the chromosomes, would the baby have 46 pairs? 92 chromosomes?

  6. Actually many traits are only on the X chromosome, ever heard of a sex linked traits? That means that it's only found on the X chromosomes.

  7. I really wonder if this is why women are more prone to autoimmune diseases than men are. After I had my son, it all went to hell.

    There is also a type of chimerism that goes from mother to fetus. This could explain so many problems.

  8. This Chimera info puts some major doubts on forensics. So a murderer for instance could actually kill someone & get away with it, if the DNA at the crime scene doesn't seem to match that of the killer. Eventually humans will develop mutant powers like the X-men.

  9. Venus is heavenly she does have a very kissable face.
    As for having kids that came from u but have DNA from different ppl – cuz she slept around. Stupid hoes need to stop sleeping with more than 1 man n vice versa

  10. Is this selective X activation why women are more likely to have natural highlights their hair than men? And on that subject, what does that mean for me as a male with natural highlights?

  11. We all contain the genetic information from more than one individual: a mother and a father. As I understand it, the scientific definition of a "chimera" deals with the fusion of a sperm and an egg from two different species. I could be wrong, of course, but I don't think so.

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