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


Calico cat

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