Why are cats white? - briefly
Cats are white due to the absence of melanin in their fur, which is a pigment responsible for color. This can be influenced by genetics or albinism, where the cat lacks the ability to produce melanin at all.
Why are cats white? - in detail
The color of a cat's fur is determined by several genetic factors and can be influenced by various environmental conditions as well. To understand why some cats are white, it's essential to delve into the science behind feline coat genetics.
Cats have two types of pigments in their fur: eumelanin (black or brown) and pheomelanin (red or yellow). The dominant gene that controls eumelanin production is called B, and its recessive allele is b. Cats with the BB genotype will have black or dark grey coats, while those with the bb genotype will lack eumelanin entirely, resulting in a red or cream coat.
However, to explain white fur specifically, we need to consider another gene: the W (white) gene. This gene is responsible for the production of tyrosinase, an enzyme crucial for melanin synthesis. If a cat inherits two copies of the recessive w allele (ww), it will lack functional tyrosinase, leading to a complete absence of both eumelanin and pheomelanin in its fur. As a result, the cat will have white fur.
Moreover, the degree of whiteness can be influenced by other genes and environmental factors. For instance, the K gene (agouti locus) controls the distribution of pigment in the hair shafts. In some cases, cats with the K^B^ allele might exhibit varying degrees of white fur due to the 'Burma' effect, where eumelanin production is restricted to the tips of the hairs, creating a diluted appearance.
Additionally, environmental factors such as temperature can impact coat color. In colder regions, it's not uncommon to find cats with white fur, which may be an adaptation to better blend in with snowy surroundings during winter months. This phenomenon is known as seasonal polymorphism and has been observed in several species of animals.
In summary, a cat's coat color is governed by multiple genetic factors, with the W gene playing a pivotal role in determining whether a cat will be white. Environmental conditions can also contribute to the development of white fur, reflecting the complex interplay between genetics and the environment in shaping feline appearances.