![]() If deactivation occurs early on each pigment cell has room to multiply into, a "red" cell will multiply into more red cells while a "black" cell will give rise to patches of black. Skin cells multiply during growth and spread out across the skin as the embryo grows the skin cells multiply. One (the "early/late deactivation theory") suggests that the time at which X chromosome deactivation occurs during foetal growth determines whether the cat has well defined patches or is brindled with intermixed black and orange hairs. There are two main theories regarding brindled torties and patched torties. ![]() Male cats only inherit one X chromosome so this is active in all skin cells as there is nothing equivalent on the Y chromosome which could "switch off" the O gene. This can only happen in cats with two X chromosomes. The skin is a mosaic of cells where some have the O gene active (making ginger pigment) and some do not (making black pigment). This occurs early on in the embryo and as skin cells multiply, they form patches. This only shows up visibly in skin cells as these produce pigment. Some cells randomly activate the O gene while others activate the gene in the equivalent place on the other X chromosome. The formation of red and black patches in a female with only one O gene is through a process known as X-chromosome inactivation. ![]() Tortoiseshell cats are therefore heterozygous (not true-breeding) for red colour. The O gene is called a sex-linked gene because it is carried on a sex chromosome. If she inherits only one O gene, she will be tortoiseshell. She must inherit two O genes to be a ginger cat. A normal male cat has XY genetic makeup he only needs to inherit one O gene for him to be a ginger cat. The O gene is carried on the X chromosome. The O gene changes black pigment into a reddish pigment. The ginger colour of cats (known as "yellow", "orange" or "red" to cat breeders) is caused by the "O" gene. Jean Bungartz referred to tortoiseshell-and-white cats as "Spanish cats" in his 1896 book "Die Hauskatze, ihre Rassen und Varietäten" (Housecats, Their Races and Varieties) in " Illustriertes Katzenbuch" (An Illustrated Book of Cats) though he said it was hard to explain why they got the name as they were not restricted to the Pyrenean peninsula. This article only considers normal tortoiseshell cats. These are discussed in detail in " Mosaicism, Tortie Tomcats, Genetically Impossible Kittens and Gender Anomalies". The very few male tortoiseshell cats are caused by genetic aberration or development abnormalities in the foetus. Wonder if these same temperamental studies can apply to kids as well?! Hmmm - something to consider.Because of the way tortoiseshell is inherited, almost all tortoiseshell and calico cats are female. ![]() Her blog " The Conscious Cat" offers more information and tidbits on this and many other facts of cats. It’s just information to help you understand what you might be up against.”Ĭurious to find out more? Award winning writer and cat expert Ingrid King,has a new book coming out called Tortitude The BIG Book of Cats with a BIG Attitude. Stelow also notes "“We are not suggesting that anyone avoid having these cats in their homes,” she said of calicos and torties. Her study, based on a survey of more than 1,200 cat owners, found that calicoes and torties are more likely to hiss, chase, bite, swat or scratch during interactions with humans". Elizabeth Stelow, a behavioral expert in the UC Davis Veterinary Medical Teaching Hospital. This research involved surveying more than 1200 cat owners with the outcome showing "research backs up long-standing observations among veterinarians that such cats often are “difficult,” said Dr. Ever wonder if coloring of fur relates to temperament of a cat? According to a recent article in the Sacramento Bee "Veterinarians from UC Davis have discovered, in recently published research, that cats with calico and tortoiseshell coat patterns tend to challenge their human companions more often than felines whose fur is less flashy". ![]()
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