Eye color
Eye color is a polygenic phenotypic character determined by two distinct factors: the pigmentation of the eye's iris[1] and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris.[2]
Etymology[edit | edit source]
The term "eye color" is derived from the combination of the English words "eye", which is from the Old English "ēage", and "color", which is from the Old English "clor".
Genetics[edit | edit source]
In humans, the pigmentation of the iris varies from light brown to black, depending on the concentration of melanin in the iris pigment epithelium (located on the back of the iris), the melanin content within the iris stroma (located at the front of the iris), and the cellular density of the stroma.[3] The appearance of blue and green, as well as hazel eyes, results from the Rayleigh scattering of light in the stroma, a phenomenon similar to that which accounts for the blueness of the sky called Tyndall effect.[4] Neither blue nor green pigments are ever present in the human iris or ocular fluid.[5] Eye color is thus an instance of structural color and varies depending on the lighting conditions, especially for lighter-colored eyes.
Eye color chart[edit | edit source]
The human eye color chart below shows the probability of eye color outcomes in children according to the eye colors of their parents. This chart is simplified and does not account for the genes of grandparents and earlier ancestors.
Parent 1 | Parent 2 | Probability of eye color in offspring |
---|---|---|
Brown | Brown | 75% Brown, 18.75% Green, 6.25% Blue |
Brown | Green | 50% Brown, 37.5% Green, 12.5% Blue |
Brown | Blue | 50% Brown, 0% Green, 50% Blue |
Green | Green | 0% Brown, 75% Green, 25% Blue |
Green | Blue | 0% Brown, 50% Green, 50% Blue |
Blue | Blue | 0% Brown, 0% Green, 100% Blue |
See also[edit | edit source]
- Iris (anatomy)
- Human genetic variation
- Population genetics
- Melanin
- Rayleigh scattering
- Tyndall effect
- Structural color
References[edit | edit source]
Eye color Resources | ||
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Contributors: Prab R. Tumpati, MD