I love weirding genetics

I recently finished discussing dosage compensation in my genetics class — you know, the way mammalian females tend to be mosaic for traits on the X chromosome because of the need to maintain a balanced dosage of gene expression for both males and females. The classic example is calico cats, which are almost always female, because the pigment gene on the X chromosome can be one of two forms, either a black allele or a yellow/orange allele, and if you’ve got two X chromosomes and are heterozygous the random inactivation of one X or the other produces a patchwork color. I hinted that there’s a way you can be a calico male, but I haven’t talked about that yet. We’ll get to chromosomal variations in a few weeks, and then I’ll give them this article to read.

The way you can get a calico male is if the cat is XXY. It’s male (usually — there are genetic variations that can change that, too!) by virtue of the Y chromosome, but it has two X chromosomes, so it also experiences randomized deactivation of one X or the other. This is just plain cool.

Except…would you believe people discriminate against cats with unusual chromosome arrangements? Of course you would. There are cat exhibitors who treat this male calico as some kind of freak. The article’s author visits a cat show to see Dawntreader Texas Calboy and his owner, Mistelle Stevenson.

I tell the people behind a registration table that I’m from D Magazine and ask where I might find an exhibitor by the name of Mistelle Stevenson.

“Oh, you’re probably here because of the calico,” says a gentleman with a helmet of silver hair, who I find out later is Mike Altschul, one of the weekend’s show managers. “Yeah, we weren’t too happy about that. She’s somewhere over there.” He flicks his hand toward a back corner. As I turn and start to walk away, he bellows after me, “You know, we don’t let three-legged cats in here either!”

I should have known then that I was stepping into some deep and dirty kitty litter.

WTF? He’s a lovely cat. And hey, why would you discriminate against three-legged cats? What’s wrong with these people?

(Note: I ask what’s wrong with these judgmental people, not what’s wrong with the cat. There is nothing wrong with the cat.)

There was nothing in the rulebook against showing male calicos, so Dawntreader Texas Calboy won a few shows, and was kicked out of a few. Then…they intentionally changed the rules to exclude him.

Then, before Calboy had another chance to compete, a sweeping addendum was made to Show Rule No. 30.01 at the CFA’s annual board meeting in February, officially making all “male cats whose color combinations occur only by virtue of genetic anomaly” ineligible from winning titles. Calboy was officially out of the competition. Stevenson was devastated. NBC 5 ran a story, which was quickly picked up by several outlets, including Newsweek. That was why, when I asked Stevenson if I could meet her at the Mesquite show in April, she said she’d be happy to talk, but Calboy would not be present. The climate was “a bit hostile.”

I’ve got news for these people. Every cat is unique, and therefore you can finagle the rules to judge any cat as a “genetic anomaly”.

As an added complication, when Dawntreader Texas Calboy grew up and became an adult, he started catting around and making kittens. This was unexpected: XXY individuals are usually sterile. Oops. So they had him tested. Another genetic surprise!

When the kittens arrived, their colors were all over the place. She wondered if maybe one of the kids let a male out of its room. There was only one way to know for sure. She swabbed the inside of Calboy’s cheek and sent it off to the Veterinary Genetics Laboratory at the University of California, Davis for testing, along with samples from two different colored kittens. They told her the sample was contaminated; Calboy’s results showed two cats. She tried swabbing again, this time videotaping the process to prove the sample was uncontaminated. Again, the lab work showed two sets of DNA. Seeing that the variants on the genes were exactly the same, the lab was able to confirm: Calboy was a chimera.

This is going to be a beautiful example for my class. I’m grinding them through the canonical rules of classical genetics, but later I’ll have to explain that sometimes you have to pay attention to the enlightening exceptions, and it’s not always as simple as you might have been taught in high school biology.


  1. birgerjohansson says

    When they say male cats cannot be calico, just say “nature will find a way”.

  2. says

    People that I must assume practice selective breeding of domesticated animals are worried about “genetic anomalies?” Seriously?
    That is one magnificent beast there.

  3. birgerjohansson says

    So Calboy is a super-cat? Have DC and Marvel been notified of this benevolent mutant?
    When his kittens come running, their owner can legitimately shout “The mutants are coming! The mutants are coming!”

  4. flexilis says

    But but but–Bastet the Great don’t make no mistakes! Callboy is clearly a work of demons!

  5. fergl says

    Another way to get a male Calico? 2 Xs with different coloured alleles plus an X/Y tranlocation in one X.

  6. timmyson says

    I feel like this is A Monty-Hall problem of Biology. “All that stuff you’re learning, that’s developing your intuition? Nature doesn’t give a hoot about that: check this out!”

    I’d love to know more about how this chimaration? chimerism? works: Are different organs or body regions one genotype (I don’t even know how to refer to the separate cat-parts which merged in utero) versus another? Is there more or less an even mix of the genotypes in each organ? Is the XXY genome sterile, and the other one the one that’s siring the kittens?

  7. moxie says

    the cat fancy people have no trouble with genetic anomalies, otherwise sphynxes wouldn’t be allowed either. they’re probably afraid male calicos are gay, or something.

  8. PaulBC says

    A dog or cat show is about the least shocking place to find this kind of essentialist thinking. Their entire business is to declare certain “breeds” real and eligible to compete, and dismiss every other entrant as anomalous. I don’t have as big a problem with this in a clearly artificial context, but it does provide a microcosm for bigotry against other humans.

  9. UnknownEric the Apostate says

    Dog and cat shows should get rid of all the “purebreeds only” snobbery crap and just be like, “Hey, here are some good dogs/cats.” More like the Puppy Bowl, less like a fascist rally, kthxbye.

  10. Eric says

    Look up Lydia Fairchild and Karen Keegan for a couple of human examples. :-)

    Kudos to Fairchild’s lawyer for figuring it out.

  11. pacal says

    I’ve heard before that Male Calico cats are unusual. But here we have a really unusual Calico cat not only not sterile but a chimera! And yes the rules of these idiotic pet shows are nonsense a lot of the time. After all these shows are one of the reasons so many dog breeds are genetic disasters.

  12. Becca Stareyes says

    @Gleigh, at 13:

    The full article says they were, which is what confirmed the chimerism, as the paternity sample kept being sent back for contamination because it contained multiple different sets of DNA. Once they accounted for the fact Calboy was a chimera, all the kittens were his. The phenotypes made no sense because some kittens got one set of genes and some got the other.

  13. raven says

    “You know, we don’t let three-legged cats in here either!”

    Stupid statement.

    All cat shows and cat breeds and cat standards are arbitrary. Cat breeds are mostly a human creation.

    Two cat breeds are due to serious deleterious genetic mutations. The hairless Siamese and the extreme flat faced Persian cats. The extremes have all sorts of health problems including with their tear ducts, nose, and even eating normal cat food.

    The Persian cat breed has been split into two because of the problems with the extremes. The older breed is now called the Classical and has a short nose but not a flat face. I don’t have problems with Persian cats like that. I even have a pure breed show Persian.
    I wouldn’t have chosen a pure breed but this one was mine the day her (elderly) owner died.

  14. magistramarla says

    We have had several Maine Coon cats in our family. We had one named Dax for 16 years. He had 7 toes (and claws!) on each front paw and 6 on his back paws. I’ve read that this mutation is frowned upon in cat shows, but seems to happen often in the breed. It didn’t matter to us – just made Dax more unique and lovable.
    We now have a Maine Coon kitten named Worf. Alas, he has the usual number of toes, but is a very lovable cat.
    We have also always had a thing for the different permutations of Siamese cats.
    Bexar was a Chocolate Point – light brown body with dark brown ears, feet and tail and blue eyes.
    Casper was a Flame Point – white body with orange ears, feet and tail and blue eyes.
    Princess Leia is a Lynx Point – a grey striped tabby with Lynx-like markings and bright blue eyes.
    All of these permutations are from cross-breeding pure bred Siamese with different colors of tabby cats.
    I’ve found that this makes for beautiful cats who are sweet, loyal pets with lovely personalities.
    We also happen to have a three-legged cat! She wasn’t born that way, though. She was a feral kitten who was found hanging by a front leg in the fence at the pool. She lost the leg due to nerve damage. She is more feral and mistrusting of her humans than PZ’s cat. However, she has a good and safe life with us and our other two cats.
    Cats rule!

  15. seattlesipper says

    A “genetic anomaly”, you say? If one wanted a contest lacking in genetic anomaly, that would be a contest of clones and not very interesting. Are we not all genetic anomalies in the great evolutionary contest, people and cats?

    I admit that it has taken me a long time to figure this out. We are, each of us, each living thing, a genetic experiment that is unique across time and space. That sounds all foofy, but I will remind you that Carl Sagan pointed out that we are all made of stardust, a grandly poetic phrasing of a scientific truth.

  16. PaulBC says


    We are, each of us, each living thing, a genetic experiment that is unique across time and space.

    I completely agree. It is a strange thing to judge an entrant to a contest based on their similarity to an ideal specimen of some imaginary category. But that’s pet shows for you.

    I hope people can learn not to do this with other human beings. Most of what we call “excellence” amounts to variance from typical expectations. So there are “good” outliers and “bad” outliers. There seems to be an inconsistency of imagining there is a pedigree with particular traits, but then imagining further that there is the specimen par excellence that isn’t really typical of the pedigree at all (or they’d all get prizes). So what is the distinction between “ideal” and “typical”? It doesn’t seem well-thought out.

  17. woodsong says

    Calboy is a beautiful beast indeed!

    I don’t have much to say about the cat-show bigotry (except HISSS, with flattened ears, bushed fur and bared fangs), but the genetics are fascinating.

    There’s a book I recommend: Cats Are Not Peas: A Calico History of Genetics by Laura L. Gould. It was first published in 1996, so my copy is a little dated, but the reprint has a section on the updated science (according the Amazon blurb. I haven’t read that edition yet.) Anyone here familiar with the book? It’s a fun read, as well as informative.

  18. says

    @19: You’re a bit of a sci-fi nerd, I take it? Because I love those cat names! (I’m thinking of naming a future kitty “Neelix” or maybe “Sukal”. For reasons.)

    I had heard that male calicos we’re exceedingly rare so this cat is an absolute treasure. Though it’s an absolute pity that some of these cat breeders are acting like the damn AKC. Ugh.

  19. rrutis1 says

    “It is a strange thing to judge an entrant to a contest based on their similarity to an ideal specimen of some imaginary category. But that’s pet shows for you.”

    It’s not so strange when you think about what we do to each other based on similarity.

  20. PaulBC says


    It’s not so strange when you think about what we do to each other based on similarity.

    Maybe not strange, but very unreliable as a heuristic.

    I’m not sure of your exact meaning, but this is an especially poor approach (IMO) to take romantically, though people do it. They concoct their “dream partner” and measure real people against this ideal. In fact, the supposed similarity is usually a lot less to the point than whether some other person feels affinity to you.

    For a more neutral example, I have worked at a lot of companies as a software engineer and had many different coworkers. I consciously work against implicit bias, since ethnic background may be the most obvious trait. But I definitely find myself automatically lumping people according to personality and work habit (quiet and reliable; crazy-fast coder who should maybe slow down; too humble; too cocky, etc.). I think it’s OK that my brain does this, because I need some kind of starting context. The risk is when someone reminds me of a person I worked with 5 years back, and I forget that he’s not the same person, so the clumsy road map I built in my head is going to frustrate me.

    Maybe these kinds of crude categories are can be thought of as initial conditions to a fixed point iteration. As events refute assumptions, you need to adjust the assumptions. No two people are alike and only a lazy person treats them as alike. The map is not the territory.

  21. PaulBC says


    I forget that he’sthey’re not the same person

    Oops… an embarrassing mistake in context and I won’t try to weasel out of it. FWIW I have worked with many woman who are software developers. I guess it says something about the biased mental image I was forming when I typed that.

  22. magistramarla says

    @25 Yes, we are sci-fi nerds! When we adopted our new Maine Coon kitten last September, we made a list of names.
    Worf, Neelix, T’ealc or Chewbacca were the contenders. My husband chose Worf, since the kitten is primarily his pet.
    Dax had been very attached to him, and losing him last May was rough. We chose Worf because he was married to Dax on DS9 and loved her very much.
    Leia is primarily my pet, and is very attached to me.