A cat’s physical traits, including its hair, are determined by its genetic makeup. The term “genotype” refers to the specific set of genes an individual possesses, acting as a blueprint for observable characteristics. This genetic foundation explains the wide array of coat types seen across cat breeds.
Genetic Fundamentals of Cat Hair
Most cats have hair, as its presence is a dominant trait. Hairless cat breeds, like the Sphynx, result from specific genetic mutations. These mutations are recessive, meaning a cat must inherit two copies of the mutated gene, one from each parent, to be hairless. For instance, a mutation in the KRT71 (keratin 71) gene is associated with hairlessness in Sphynx cats. A cat with at least one dominant allele for hair will develop a coat, even if it carries a recessive hairless allele. Cats with one dominant and one recessive allele are carriers; they have hair but can pass the hairless trait to offspring. Thus, two haired carriers can produce hairless kittens.
Determining Hair Length
Hair length in cats is controlled by the Fibroblast Growth Factor 5 (FGF5) gene, which has alleles determining short or long hair. The allele for short hair is dominant, while the allele for long hair is recessive. For a cat to have long hair, it must inherit two copies of the recessive long-hair allele. Cats with at least one dominant short-hair allele will display short hair, even if they carry a long-hair allele. For example, American Shorthairs typically have the dominant short-hair genotype, while Maine Coons possess the recessive genotype for long hair.
Exploring Hair Texture and Type
Beyond presence and length, other genes influence hair texture and type, leading to curly, wavy, or wiry coats. The KRT71 gene, which influences hair presence, also plays a role in some curly-coated breeds. For instance, a different recessive mutation in the KRT71 gene causes the curly coat in Devon Rex cats. The Selkirk Rex breed, known for its plush, curly coat, results from another distinct gene mutation, which is autosomal dominant. The wire-like hair of the Lykoi cat is linked to specific genetic factors that alter hair follicle structure, leading to its distinctive appearance.
Genotypes and Cat Breeds
The distinct appearance of various cat breeds often arises from specific combinations of these hair-related genotypes. For example, a Sphynx cat carries two copies of the recessive hairless allele (hr/hr) at the KRT71 locus, resulting in its characteristic lack of fur. A Maine Coon typically has two copies of the recessive long-hair allele (l/l) for the FGF5 gene, giving it a flowing, long coat. A Devon Rex, while short-haired, possesses two copies of a specific recessive KRT71 mutation that results in its curly coat. Understanding these genotypes helps responsible breeders predict offspring traits and manage genetic health, ensuring desired characteristics and avoiding unintended ones.