Eye pigment, which determines the color of the eyes, is primarily determined by the amount and distribution of melanin, a pigment produced by specialized cells called melanocytes. Melanin is also responsible for the color of the skin and hair.
Key points about eye pigment and melanin include:
1. **Melanin Production**: Melanin production is regulated by genetic factors and influenced by environmental factors such as exposure to sunlight. The amount of melanin produced by melanocytes in the iris of the eye determines the eye color.
2. **Types of Melanin**: There are two main types of melanin that contribute to eye color:
– **Eumelanin**: This type of melanin is responsible for brown and black colors. Higher concentrations of eumelanin result in darker eye colors, such as brown and black.
– **Pheomelanin**: This type of melanin is responsible for red and yellow colors. Lower concentrations of eumelanin and higher concentrations of pheomelanin result in lighter eye colors, such as blue and green.
3. **Genetic Variation**: Eye color is inherited from parents through the interaction of multiple genes. The genetics of eye color are complex, with variations in genes such as OCA2, HERC2, and TYR influencing the amount and distribution of melanin in the iris. Different combinations of these genes can result in a wide range of eye colors, including brown, blue, green, hazel, and gray.
4. **Changes Over Time**: Eye color can change over time due to factors such as aging, hormonal changes, and exposure to sunlight. Babies are often born with lighter eye colors that may darken or change as they grow older. However, once eye color is established in adulthood, it tends to remain relatively stable.
While melanin is the primary determinant of eye color, other factors such as structural properties of the iris, lighting conditions, and individual variations in pigmentation can also influence the appearance of eye color. Overall, eye color is a complex trait influenced by both genetic and environmental factors.