Regard to the OP, Calico cats are often used as an example of the Lyon hypothesis of gene inactivation. If a female cat has two X chromosomes and a male cat has only one X, there needs to be a way to ensure that females ‘don’t express X chromosome genes at twice the level of males (having twice the number of genes)’. One of the X chromosomes in females is inactivated and becomes a so-called Barr Body-it isn’t expressed, so now females would have one active X, just like males.
The inactivation of one X or the other in females is random in early embryonic development. If one X has the allele for, say, black pigmentation and the other X has the allele for orange, these colors will be expressed in all the descendent cells that produce fur according to which X was inactivated-resulting in the mosaic of different colored patches of fur seen in the Calico cat. Genes for other colors are present on non-sex chromosomes, so it becomes more complicated than just which X becomes a Barr Body.
I know, I know, I’m a little behind in the thread, but this question is the whole reason I registered in the first place…
All the male oange (yellow, ginger, etc…) tabby cats I have ever known were male, and I have only recently heard of (sterile) male calicos.
I <i>have</i> however, beenn led to believe that if a calico, (female,) and an orange tabby, (male, were bred, the results would be a litter in which all females were calico, and all males were ginger-toms.
After wading through the many genetics posts, I would assume that would be a natural result of the x/y, recessive/dominant combination, though I have been told that ginger and calico are essentially the same breed, thus the results would be the same as breeding a pair of Siamese, or a pair of Russian Blues.
Anyone care to enlighten this er… genetically challanged… Lynxgyrl?
Interesting. George, my parents’ ginger tabby, might have calico sisters? BTW, everyone who sees George thinks that he’s absolutely the cutest thing alive.
Great site, and it cleared something up for me. I’m looking at my pretty calico as I write this. She’s female, but I’ve heard that calicos can be male, and can also be fertile. The above site confirmed this.
Here’s how “linked” traits were explained to me. The genome is a long chain of genes, like the alphabet is a long chain of letters. Picture the mother and father’s genomes as two copies of the alphabet:
When the two mate, their genes are split up and recombined randomly in the offspring (not really randomly, I know, but bear with me in the analogy). The gene for femaleness is near the gene for caliconess, just like the letter “A” is near the letter “B.” If you took some scissors to the alphabet above and chopped it at random places several times, you’d get a mixing of the parents’ traits, but most of the time the “A” and “B” will stay together.
It’s not impossible to separate “A” from “B”, and in fact statistically it MUST happen on occasion. But it won’t happen often.
I believe the principal is the same. BTW, I’m very fond of both calicos and torties (have had both kinds in my life) and have noticed that they seem to have very unusual personalities, as well. My vet says the mixed up genetics thing=mixed up personalities.
I’ve owned a calico as well, and her offspring were tortoise shell and tabby.
Suffice it to say, that the momma calico went nuts after a second-litter mixup, the two remaining cats in our family(a tortoise shell, and my Tabby, aptly named “Killer”), both have some interesting quirks. Mainly anti-socialism, and I suspect depression…
Actually, Dachshunds (including the one chewing on my toes right now) are bred to be short, so they can chase critters (specifically badgers) down a hole. The cats are bred with short legs because it looks funny, and people like funny-looking animals ;).
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By “unusual personalities”, do you mean that they’re evil, psychopathic, antisocial monsters? Every calico that I’ve ever known has been like that. On the other hand, the supposedly unlucky black cats seem to have a disproportionate tendancy to friendliness.
"Here’s how “linked” traits were explained to me. The genome is a long chain of genes, like the alphabet is a long chain of letters. Picture the mother and father’s genomes as two copies of the alphabet:
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZ
When the two mate, their genes are split up and recombined randomly in the offspring (not really randomly, I know, but bear with me in the analogy). The gene for femaleness is near the gene for caliconess, just like the letter “A” is near the letter “B.” If you took some scissors to the alphabet above and chopped it at random places several times, you’d get a mixing of the parents’ traits, but most of the time the “A” and “B” will stay together. "
Five, your explanation of how linked genes work is right on. However, calico cats are not the result of this phenomenon. To start, there is no gene for “femaleness”. An animal will be female if there is no functional Y chromosome present (specifically the Sry gene). Under normal circumstances an animal will be either XX (female) or XY (male). The XX have no Y chromosome and thus develop as females. The X chromosome also carries the gene coding for either orange or black pigmet (one or the other, not both). In order for an animal to get both black and orange fur it needs to have 2 X chromosomes. This situation (XX) is normally only found in female animals. The exception is when you get the unusual case of an XXY individual. It is possible for these animals to have both black and orange pigment. They will also develop as males since they have the Y chromosome. They are also usually (but not always) sterile as a result of their abnormal chromosome arrangement.
Are you still paying attention? I will be quizzing you on these subjects tomorrow.
John
OK, let’s assume the genes on the X c’some are the only ones controlling this (Oh, BTW, white bellies, found on all these colorations, is another gene entirely, before anyone asks.) which could be very wrong.
The father cat would then have X(orange)Y and the mother would have X(orange)X(black). Sons would then get the Y from the father and one of mom’s Xs, so half would be black and half would be orange. Daughters would get dad’s orange X and one of mom’s Xs. So half would be X(orange)X(orange) = all orange fur, and half would be X(orange)X(black) = calico.
Again, without researching it I can’t guarantee there aren’t other genes affecting the outcome, but that’s how it would be if there aren’t. Simple high school Mendelian genetics. Huzzah.
