Why does a cat have blue eyes? - briefly
Cats can have blue eyes due to a lack of melanin in the iris, which scatters light back in a way that makes the eye appear blue. This is often seen in cats with certain genetic conditions or in breeds specifically selected for blue eyes.
Why does a cat have blue eyes? - in detail
Cats are known for their captivating eye colors, with blue being one of the most striking and intriguing. The development of blue eyes in cats is influenced by several genetic factors and can be traced back to the presence or absence of specific pigments in the iris.
The primary factor determining a cat's eye color is the amount and type of melanin present in the iris. Melanin is a pigment that comes in two forms: eumelanin, which is responsible for brown and black colors, and pheomelanin, which contributes to red and yellow hues. The absence or low concentration of melanin leads to blue eyes.
In cats, the gene responsible for eye color is located on chromosome E. This gene, known as O (Orange), has two main alleles: O (dominant) and o (recessive). The O allele is associated with eumelanin production, resulting in green or gold eyes, while the o allele leads to a lack of eumelanin, resulting in blue eyes.
Additionally, the B (Brown) gene plays a significant role in modulating eye color. This gene has two alleles: B (dominant) and b (recessive). The B allele increases the production of eumelanin, often leading to brown or amber eyes, while the b allele reduces eumelanin production, favoring blue eyes.
The combination of these genetic factors determines the final eye color in cats. For instance, a cat with the genotype ooBB will have blue eyes because the recessive o alleles prevent eumelanin production, and the dominant B alleles do not significantly increase it. Conversely, a cat with the genotype OObb will have green or gold eyes due to the presence of eumelanin from the dominant O alleles and the reduced melanin production controlled by the recessive b alleles.
It is essential to note that not all blue-eyed cats are homozygous for the o allele (oo). Some may have a combination of genes that results in a dilution of eumelanin, such as the D (Dilute) gene, which can also contribute to the development of blue eyes.
In summary, the blue color in a cat's eyes is primarily due to the absence or low concentration of melanin, particularly eumelanin, in the iris. This is governed by the specific genetic combinations involving the O and B genes, which dictate the production and distribution of pigments in the eye.