Tortoiseshell cat’s genetics

Tortoiseshell cats are named for their bi-colored coats that look like the shell of a tortoise. Affectionately referred to as “torties,“ these colorful kitties are favorite pets in many homes. They have such interesting and unique coats that it’s often the first thing people comment on when they see your cat. You might be wondering how they have evolved to have such gorgeous markings. Much like calico cats, tortoiseshell cats have some pretty interesting genetics, and they’ve become mainstays in folklore all over the world. Thanks to a number of genetic mutations, their coats develop with almost marbled patterns. Whether you’re considering adopting a tortoiseshell or just want to learn more about these fun and frisky cats, these facts and photos are sure to delight. The distinctive feature of a tortoiseshell is the patterned coat—not the breed. A tortoiseshell breed of cat doesn’t actually exist. Several breeds, however, can exhibit tortoiseshell markings, such as American shorthair, British shorthair, Cornish Rex, Persian, and Maine Coons, among others. Although tortoiseshell coats are most commonly a ginger red and black, they can also have hints of cream, orange, or gold. The colors in their coats are either “bridled“ and look like they’re woven together, or “patched,“ which means the colors form in large patches all over the body. Like calico cats, you’ll find most tortoiseshell cats are female. That’s because the same chromosomes that determine their sex also determine the colors in their coats. The female sex chromosome (X) also carries the genetic code for orange or black coat colors; the male sex chromosome (Y) does not carry information on coat color. Because females have two X chromosomes, they have two sets of genetic information that can determine their coat color. The embryo shuts off one X chromosome in each cell, resulting in orange and black color variations in their coats. Because a male cat has one X chromosome and one Y chromosome, he’ll only be orange or black—not both. In very rare cases—about 1 in 3,000—a male tortoiseshell cat can be born with two X chromosomes and one Y chromosome.1 Unfortunately, male cats with XXY Syndrome are sterile and often have serious health issues, resulting in significantly shorter lifespans than female torties. Tortoiseshell cats aren’t a specific breed, but some believe they have a specific temperament. In a study conducted by UC Davis Veterinary Medical Teaching Hospital, researchers pondered the link between a domestic cat’s coat color and its behavior. Tortoiseshell cats (along with calicos and “torbies“) were the main focus of the study.3 After the study was published, word spread that tortoiseshell cats have a distinct, somewhat sassy temperament, which was quickly coined “tortitude.“ And, anecdotally, many tortie parents agreed that their cats were high-energy, sassy, and even slightly aggressive. But concluded in the study results, researchers actually didn’t find a distinct link between coat color and behavior, temperament, or personality.3 Maybe “tortiude“ was just confused with regular old cases of catitude. Many countries have auspicious legends about tortoiseshell cats. According to folklore from Southeast Asia, tortoiseshell cats were formed from the blood of a young goddess. In Japan, it’s believed that tortoiseshell cats can help protect the home from ghosts. English folklore says rubbing a tortoiseshell cat’s tail on a wart will cure the affliction. In the United States, tortoiseshell cats are believed to be “money cats“ that will bring good fortune into the home. #tortoiseshellCats #catsBriding #genetics #biology #furColor