Calico cat
Calico cats are domestic cats with a spotted or parti-colored coat, usually predominantly white with orange and black patches. Outside of North America the pattern is more usually called tortoiseshell-and-white. In the province of Quebec, they are unofficially considered a breed by the french-speaking population and called chatte d'Espagne (French for 'Spain's female cat').[1] Other names include tricolor cat, mi-ke (Japanese for 'triple fur') and lapjeskat (Dutch for 'patches cat'); calicoes with diluted coloration have been called calimanco or clouded tiger. Calicoes differ from simple tortoiseshell cats in that tortoiseshell cats have black and orange coats with possible patches of white, whereas calico cats have white-based coats with black and orange patches.[2] Some calico coats have a swirl (called a rosette) on either side of the stomach.[3]
"Calico" refers only to a color pattern on the fur, not to a breed. It is absent from lists of breeds.[4] 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 sex chromosome, calicoes are nearly always female.[5]
Historical background
Historical migration
As calico cats are not a breed, but a color pattern on the fur which occurs in a non-predictive manner, there is no true historical background concerning calico cats. 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 France and Italy, originating from Egypt.[6]
Discoveries
The beginning of serious study of calico cats seems to have occurred around 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.[7] In 1959, Japanese cell biologist Susumu Ohno determined the Barr bodies were X chromosomes.[7] In 1960, Mary Lyon proposed the concept of X-inactivation: one of the two X chromosomes inside a female mammal shuts off.[7] She observed this in the coat color patterns in mice.[8] Although study has continued and deepened, these were the major contributors in the discovery of X inactivation in the early days.
Genetics
General genetics
Mammals have two sex chromosomes: the X chromosome and the Y chromosome. A normal female has two X chromosomes and no Y chromosomes and normal males have one X chromosome and one Y chromosome. It is the chromosome that comes from the father which determines the sex of the mammal. The father will either contribute his X chromosome whereby the offspring will be female or his Y chromosome and the offspring will be male.[2]
All female placental mammals seem to have a common trait: they are all mosaics. They all have random patches of X inactivation from one of their two X chromosomes.[7] This inactivation occurs early in cell development, is random, and is permanent.[9]
Genetics of calico cats
Calico cats are almost always female because the X chromosome determines the color of the cat and a female cat has two X chromosomes. A common male cat has one X and one Y chromosome. Since the Y chromosome does not have any color genes, there is no chance he could have both orange and non-orange together. One main exception to this is when, in rare cases, a male has XXY chromosomes, in which case the male could have tortoiseshell or calico markings. Most male calico or tortoiseshell cats are sterile due to the abnormality of carrying two X chromosomes.
"In the case of a calico cat, the feline’s parents passed on different versions of X chromosomes genes related to coat color."[7] The color of calico or tortoiseshell cats is determined by the X chromosome(s). Tortoiseshell and calico cats are almost always female because of X chromosome inactivation.[10][11]
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 genes for a black or white coat on the other, and those can affect or modify the orange mutant gene. 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 (although some modifier genes can add a bit of white here and there), but unless he has a chromosomal abnormality he cannot be a calico cat."[6]
Current issues
It is 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."[12]
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 mammal.[7][9][13]
Folklore
Cats of this coloration are believed to bring good luck in the folklore of many cultures.[14] In the United States, these are sometimes referred to as money cats.[15] The Japanese Maneki Neko figurine is almost always a calico cat.
See also
References
- ^ "La chatte d'Espagne" Web. <http://membres.multimania.fr/catsmine/races/espagne.htm>
- ^ a b Robinson, Richard. "Mosaicism". Genetics. New York: Macmillan Reference USA, 2003. 76-80.
- ^ Random House Webster's College Dictionary. New York: McGraw-Hill, 1991. Print.
- ^ Marilyn Menotti-Raymond, Victor A. David, Solveig M. Pflueger, Kerstin Lindblad-Toh, Claire M. Wade, Stephen J. O’Briena, Warren E. Johnson. “Patterns of molecular genetic variation among cat breeds.” Science Direct. 17 August 2007. Web. <http://home.ncifcrf.gov/ccr>.
- ^ "Calico cat." Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica, 2010. Web. 6 June 2010 <http://www.search.eb.com/eb/article-9471963>.
- ^ a b Hubbell, Sue. Shrinking the Cat: Genetic Engineering before We Knew about Genes. Boston: Houghton Mifflin, 2001.
- ^ a b c d e f John Travis. "Silence of the Xs". Science News. 158 (6): 92–94. 5 August 2000.
- ^ Gilbert, Scott F. "Transcriptional Regulation of an Entire Chromosome: Dosage Compensation." Developmental Biology. Sunderland, Mass.: Sinauer Associates, 2000. Print.
- ^ a b Gunter, Chris. "She Moves in Mysterious Ways". Nature 17 March 2005.
- ^ Lyon, M.F. (2001). "Tortoiseshell coloring". In Brenner, Sydney (ed.). Encyclopedia of Genetics. Amsterdam: Elsevier. pp. 1970–1971. doi:10.1006/rwgn.2001.1296.
- ^ "X Inactivation". Howard Hughes Medical Institute, 5 October 2009. Accessed 22 May 2010.
- ^ Tsernoglou, Penelope Ann. "To Clone or Not to Clone: A Look at Why Cloning Fluffy and Fido Might Not Be in the Best Interests of Society and May Inevitably Pave the Way for Human Cloning." 25 Apr. 2004. Web. 24 Apr. 2010. <http://www.law.msu.edu>.
- ^ Pearson-White, Sonia. "Mammalian Genetics: X/imprinting". The University of Virginia. 2004. Accessed 23 May 2010.
- ^ Hartwell, Sarah (1995). "Feline Folktails - Cats in Folklore and Superstition". Retrieved 22 January 2009.
- ^ Finegan, Edward; Rickford, John (2004). "Language in the USA: Themes for the Twenty-first Century". Cambridge University Press. Retrieved 22 January 2009.
