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Anonymous File :-(, x)
>>58959 >>58957 >>58955
The reason why male calicos are extremely rare is because fur color is partially determined by the sex chromosomes, and 3 colors can only appear in the female's set of sex chromosomes. For a male to have 3 colors actually means its kind of female, which is why when there IS a male calico, he's often sterile. That is the short answer.
Here is the long answer: Fur pigment is partially determined by the X chromosome. In order for there to be 3 colors present (orange, black, and white) one X chromosome must have the gene for orange pigment, and the other X chromosome must have the gene for black pigment. White fur is actually a lack of pigment, and is controlled by a completely different chromosome, which I will not get into.
Since there must be 2 X chromosomes present in a calico, and because only females have 2 X chromosomes, all normal calicos are female. However, if a "male" calico has a genetic defect causing the karyotype XXY (similar to Klinefelter's syndrome in humans), then it is possible for both orange and black to be present. This defect is extremely rare, and will usually cause sterility.
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