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Saturday, November 25, 2006

Calico Cats


One X Chromosome Is Inactivated in Mammalian Females by Condensation into Heterochromatin



[Calico_cat_Phoebe is from Free Software Foundation.]


  1. Ah yes. Weekend cat blogging, Moran-style.

    Thanks! I happen to know a Calico. Most people think she's cuter!

  2. A couple of pesky questions from a non-biologist:

    Does random deactivation of one X in humans mean that in a very minor sense, all women are chimeras?

    And what about tortoise shell cats? Are they all female?

  3. Another pesky question:

    What controls the stripes on tabby cats?

  4. Pesky question #4:

    What about 2-color cats? I've mostly seen black-and-white ones, but I used to be the pet human and devoted servant of one (male) who was orange-and-white, and I've also seen lots of tabby-and-white ones.

    Pesky question #5:

    Why are 2-color and tabby cat markings so symmetrical?

  5. Yes, all women are chimeras. It explains a lot .... :-)

    Tortoise shell cats are the same as Calico cats.

    I don't know anything more about the genetics of coat color in cats. Perhaps someone else will respond.

  6. Darn, I had to study from your book, too (got an A+ though so it ended well...LOL)

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  9. [You know how stuff just pops into your head at 3 am? I just realized that my next-to-last post had a major boneheaded goof in it - and so did the last one. So I'm trying again.]

    "Yes, all women are chimeras. It explains a lot"

    =LOL= And all this time I thought it was just because I'm bipolar. Just one more way in which my Two-Headed Monster avatar fits, I guess. =grin=

    OK. Leaving aside the autosomes for the moment (pesky autosomes, they complicate everything! =another grin=):

    In effect, we women end up with half-and-half "mom X's" and "dad X's," while men have only "mom X's." If we have half our working X's from each parent and men have all their X's from mom (on top of which there's far less genetic information on the Y than the X, AFAIK at least), could it be said that in developmental terms we're "related" to our moms and dads to a very slightly different degree (or at least in a different way) than our brothers are?

    And what happens to the Y chromosome as males develop? Does it stay active alongside the X?

    Am I confused enough yet? =yikes!= and =grin= simultaneously (There goes my Two-Headedness again!) Well, I did say at the outset that I'm not a biologist! I'd better quit before I get any further behind!

    "Tortoise shell cats are the same as Calico cats."

    That's what I thought, but I wasn't 100% sure. I don't recall ever having seen a male tortie. I've known some real sweetheart tortie ladies though - a gray tortie once graciously condescended to allow me and my (now former) Significant Other to share her living space.

    Come to think of it, the last cat who adopted us was gray-and-tan too - a light calico who evidently got fed up with living in another apartment with about 6 other cats, some of whom were meaner than dirt when it came to others of their species.

    She walked into our place one day while we were moving stuff in, curled up in the sunny spot on top of the dining-room radiator and zonked out, and that was that. She'd been an indoor-outdoor critter all her life, but we could never get her to even think about going outside and possibly meeting up with one of the meanies.

    Fortunately, her former pet human was OK with it!

    "I don't know anything more about the genetics of coat color in cats. Perhaps someone else will respond."

    I hope so. I've been fascinated by genetics ever since I was a little kid. I discovered Mendel's experiments one day while looking through my dad's college biology textbook. I must have been about 7 at the time, but 45+ years later I still remember that first "wow, that's so neat!" moment.

    (Back to those pesky complicated autosomes: I'm the oldest of 4 blood siblings. Except for the fact that 3 of us have brown hair, we look almost nothing alike. My mom says, "You all look like you came from the adoption agency!")

  10. I've been carrying a link to this as a draft for months and only now got around to publishing it. For some reason it doesn't appear in "Links to this post" - so here it is: "Sandwalk on Calico Cats".

  11. I have a calico cat too. And it's female.But My friend at squidoo has a male calico. here are my lens about calico cat My pet

  12. I don't understand much about genetics and biochemistry, but I know that calico cats are very cute and adorable. :)

  13. Specifying and sustaining pigmentation patterns in domestic and wild cats

    Genetics of Pigmentation in Dogs and Cats

    Both articles are free.