Eye color inheritance patterns result in physical traits determined by the genetics of both parents, and are specifically expressed by pigmentation of the iris which surrounds the pupil in the eye, combined with the amount of light that reflects off the iris. The color of the iris ranges on a continuum from very light blue in color to very dark brown in color, with brown-eyed individuals having large amounts of a protein called melanin on the surface of the iris and blue-eyed individuals having little melanin on the surface of the iris.
“Scientifically, eye color is often described as blue, green, or brown.”
Eye color does not follow the basic inheritance pattern explained away using simple Mendelian genetics. Instead, the inheritance pattern of eye color is polygenic, meaning color is determined through the complex interaction amongst multiple genes. While a child’s eye color may be predicted in considering the eye colors of the child’s parents, genetic variation may lead to unexpected results.
Today, scientists recognize more than a dozen genes involved in the physical display of eye color. The two most important genes, HERC2 and OCA2, are located on chromosome 15 and play a major role in the development of eye color. In addition, several other genes play more limited roles in determining eye color. Combined, the interactions amongst all the known genes contributors to eye color create the continuum of eye color seen in individuals.
While eye color inheritance patterns are not definitively predictive, scientists are slowly unraveling the complexity of the genes attributed to eye color. Meanwhile, if you have questions, feel free to contact a genetic counselor or speak with your reproductive endocrinologist about the genetics of eye color.