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Calico cats are domestic cats with a spotted or parti-colored coat that is predominantly
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white, with patches of two other colors. Outside of North America, the pattern is more usually
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called tortoiseshell-and-white. In the province of Quebec, they are sometimes called chatte
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d'Espagne cat of Spain'). Other names include brindle, tricolor cat, mi-ke, and lapjeskat;
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calicoes with diluted coloration have been called calimanco or clouded tiger. Occasionally,
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the tri-color calico coloration is combined with a tabby patterning. This calico patched
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tabby is called a caliby.
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"Calico" refers only to a color pattern on the fur, not to a breed. It is absent from
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lists of breeds. Among the breeds whose standards allow calico coloration are the Manx, American
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Shorthair, British Shorthair, Persian, Japanese Bobtail, Exotic Shorthair and Turkish Van.
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Because genetic determination of some coat colors in cats is linked to the X chromosome,
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calicoes are nearly always female. Because of the genetics involved, calico males are
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rare, and generally have impaired vitality and are almost always sterile.
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History The coat pattern of calico cats does not define
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any breed, but occurs incidentally in cats that express a range of color patterns; accordingly
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the effect has no definitive historical background. However, the existence of patches in calico
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cats was traced to a certain degree by Neil Todd in a study determining the migration
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of domesticated cats along trade routes in Europe and Northern Africa. The proportion
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of cats having the orange mutant gene found in calicoes was traced to the port cities
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along the Mediterranean in Greece, France, Spain and Italy, originating from Egypt.
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Genetics
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In genetic terms calico cats are tortoiseshells in every way, except that in addition they
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express a white spotting gene. There is however one anomaly: as a rule of thumb the larger
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the areas of white, the fewer and larger the patches of ginger and dark-or-tabby coat.
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In contrast a non-white-spotted tortoiseshell usually has small patches of color or even
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something like a salt-and-pepper sprinkling. This reflects the genetic effects on relative
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speeds of migration of melanocytes and X-inactivation in the embryo.
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Serious study of calico cats seems to have begun about 1948 when Murray Barr and his
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graduate student E.G. Bertram noticed dark, drumstick-shaped masses inside the nuclei
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of nerve cells of female cats, but not in male cats. These dark masses became known
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as Barr bodies. In 1959, Japanese cell biologist Susumu Ohno determined the Barr bodies were
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X chromosomes. In 1961, Mary Lyon proposed the concept of X-inactivation: one of the
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two X chromosomes inside a female mammal shuts off. She observed this in the coat color patterns
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in mice. Calico cats are almost always female because
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the locus of the gene for the Orange/non-orange coloring is on the X chromosome. In the absence
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of other influences, such as color inhibition that causes white fur, the alleles present
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in those orange loci determine whether the fur is orange or not. Female cats — like
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all female placental mammals — have two X chromosomes. In contrast, male placental
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mammals, including chromosomally stable male cats, have one X and one Y chromosome. Since
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the Y chromosome does not have any locus for the orange gene, there is no chance that such
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a male could have both orange and non-orange genes together, which is what it takes to
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create tortoiseshell or calico coloring. One exception is that in rare cases faulty
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cell division may leave an extra X chromosome in one of the gametes that produced the male
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cat. That extra X then is reproduced in each of his cells, a condition referred to as XXY.
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Such a combination of chromosomes could produce tortoiseshell or calico markings in the male,
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in the same way as XX chromosomes produce them in the female.
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All but about one in three thousand of the rare calico or tortoiseshell male cats are
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sterile because of the chromosome abnormality, and breeders reject any exceptions for stud
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purposes because they generally are of poor physical quality and fertility. In any event,
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an fertile XXY male could not normally pass on any of those X chromosomes to any male
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offspring, so his male kittens would practically always be normally coloured, either ginger
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or non-ginger, but not tortoiseshell or calico. As Sue Hubble stated in her book Shrinking
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the Cat: Genetic Engineering before We Knew about Genes,
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"The mutation that gives male cats a ginger-colored coat and females ginger, tortoiseshell, or
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calico coats produced a particularly telling map. The orange mutant gene is found only
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on the X, or female, chromosome. As with humans, female cats have paired sex chromosomes, XX,
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and male cats have XY sex chromosomes. The female cat, therefore, can have the orange
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mutant gene on one X chromosome and the gene for a black coat on the other. The piebald
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gene is on a different chromosome. If expressed, this gene codes for white, or no color, and
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is dominant over the alleles that code for a certain color, making the white spots on
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calico cats. If that is the case, those several genes will be expressed in a blotchy coat
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of the tortoiseshell or calico kind. But the male, with his single X chromosome, has only
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one of that particular coat-color gene: he can be not-ginger or he can be ginger, but
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unless he has a chromosomal abnormality he cannot be a calico cat."
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It is currently impossible to reproduce the fur patterns of calico cats by cloning. "This
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is due to an effect called x-linked inactivation which involves the random inactivation of
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one of the X chromosomes. Since all female mammals have two X chromosomes, one might
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wonder if this phenomenon could have a more widespread impact on cloning in the future."
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Calico cats may have already provided findings relating to physiological differences between
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male and female mammals. This insight may be one day broadened to the fields of psychology,
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psychiatry, sociology, biology and medicine as more information becomes available regarding
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the complete effect of random X-inactivation in female mammals.
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Folklore Cats of this coloration are believed to bring
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good luck in the folklore of many cultures. In the United States, these are sometimes
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referred to as money cats. The Japanese Maneki Neko figurine is almost always a calico cat.
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A cat of the calico coloration is also the state cat of Maryland in the United States.
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See also Bicolor cat
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Point coloration Tabby cat
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Maltese cat Deaf white cat
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Cat coat genetics Tortoiseshell cat
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The Cat Who Went to Heaven References