The Genetic Rarity of Male Calico Cats

     The article, 'Why Are Male Calico Cats So Rare', discusses the uncommon genetic abnormality of male calico or male tortoiseshell cats. So much so that the chances of a calico cat being a male is estimated to be one in three thousand. Calico cats do not describe the cat breed, but rather the feline's coat; typically a calico has a tricolor coat, white, cream, and gray or white, orange, and black, and a tortoiseshell coat has two colors black and orange marbled.  It has been found that coat color is coded in specific chromosomes referred to as a sex-linked trait. For example, both male and female felines could have an orange coat (the X chromosome carrying the black gene becomes inactivated creating orange fur) or a black coat (vice versa if the chromosome carrying the orange gene on the X chromosome becomes inactivated creating black fur) because the gene that controls both of these color patterns is found on the X chromosome. Biologically, females have two X chromosomes, while males have an X and Y chromosome. Since female felines have XX chromosomes, a female cat will easily express the mixed color pattern of both black and orange with a higher percentage of X chromosomes in their genome compared to male cats.  This results in a more apparent or visible mottled effect due to the higher "concentration" of X chromosomes in females.  Whereas, male felines with an XY chromosome, can only have a black or orange coat; unless they have a genetic abnormality that is known to increase the number of X chromosomes. Typically described as Klinefelter syndrome, a syndrome that can be observed in both humans and animals, where a male has three sex chromosomes, XXY. This XXY combination could be a result of the incomplete separation of the paternal chromosome pair during the time of fertilization. This XXY combination, likewise in humans, results in malformed sexual organs, typically resulting in male calico and tortoiseshell cats being sterile. 

    Male calico/tortoiseshell felines, meaning cats with Klinefelter syndrome, have been found to have a higher risk of developing health problems, potentially decreasing their life span when compared to the average tomcat. Some of these health problems are as listed: increased body fat, leading to diabetes, joint pain, heart disease, kidney disease, hypertension, and even certain types of cancer. 

   I chose this article topic because I have a female calico kitten, and as mentioned above, I was aware that, typically, calicos and tortoiseshell cats are females. Females can display both colors in a calico or tortoiseshell pattern since they have two X chromosomes (multiple colors/patterns of black, orange, and white, or grey, cream, and white). However, males, with only one X chromosome, do not express this mottled color pattern described above as noticeably. While I am aware that some multicolored tomcats exist, I did not realize how this was possible with the involvement of the X chromosome. Although this article does not go into the research that was conducted to support these findings, I find the information interesting, especially when I look at my female dilute calico kitty.

p.s. *from the article* Apparently, in many cultures, calico and tortoiseshell cats are coined with the nickname "money cats," as they are believed to bring money, wealth, and good luck to any families who adopt them! Which is something I have never known before!