Why do Siamese cats have blue eyes? - briefly
Siamese cats have blue eyes due to a genetic mutation affecting the tyrosinase enzyme, which reduces melanin production in their eyes, resulting in their distinctive blue coloration.
Why do Siamese cats have blue eyes? - in detail
The striking blue eyes of Siamese cats are a result of a genetic mutation that affects pigmentation. This mutation is linked to the gene responsible for albinism, specifically the tyrosinase enzyme, which is crucial for melanin production. In Siamese cats, a temperature-sensitive form of this enzyme causes partial albinism, meaning melanin is only produced in cooler areas of the body, such as the ears, face, paws, and tail. The warmer parts, including the eyes, remain devoid of melanin. The absence of melanin in the iris allows light to scatter and reflect in a way that produces the characteristic blue color. This phenomenon, known as the Tyndall effect, is similar to how the sky appears blue. The blue eye color in Siamese cats is thus a direct consequence of their unique genetic makeup and the temperature-dependent expression of their pigmentation genes. This trait has been selectively preserved and is now a defining feature of the breed.