They can’t be bred to produce more male tortoiseshell or calico cats, which is in part why these cats are rare to find.īut make no mistake-there is utility in neutering sterile male tortoiseshell cats. In exchange for the rare male tortoiseshell pattern, Klinefelter males are typically sterile from an imbalance of sex hormones. Some may be mosaics, which means the XXY condition happens after conception, and the cat is a mixture of cells with different numbers of X chromosomes. Some male tortoiseshell cats may be chimeras, which result from fusion during early development with different color genotypes. These males are known as Klinefelter males, named for endocrinologist Harry Klinefelter who first identified this condition in the 1940s. If a male cat has XXY chromosomes, he can be male and still have the required X chromosomes to make a tortoiseshell pattern. Genetic anomalies do occur, however, leading to a cat having three chromosomes. Image By: andy-holmes, Unsplash How Can Males Be Tortoiseshell?Ī cat must have XX chromosomes (female) to be a Tortoiseshell cat. Females have more opportunities to have variations that include the color orange. In fact, there was a longstanding belief that only male cats can be orange tabbies, when it’s just more common. Females have XX chromosomes while males have XY chromosomes, which is why both males and females can be orange.įemales, however, are more commonly calico, tortoiseshell, or orange tabby colored, whereas most male cats are orange tabby. The primary gene for coat color, B, can be masked by the co-dominant gene for orange color, which comes from a gene in the X chromosomes. Leonard Doncaster was a geneticist who first proved the tortoiseshell is a female heterozygote of orange and black with the corresponding male will be orange. Some cats have a “split-face” pattern with black on one side and orange on the other with a defined line. Sometimes, tabby patterns with black, brown, or red are seen. Dilution genes can change the dominant colors to cream and blue, lilac and fawn, or other light colors.
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