Eye Color Genetics

The eye speaks with an eloquence and truthfulness surpassing speech. It is the window out of which the winged thoughts often fly unwittingly. It is the tiny magic mirror on whose crystal surface the moods of feeling fitfully play, like the sunlight and shadow on a still stream. ― Henry Theodore Tuckerman

The placement of our eyes - in the uppermost part of the body and that too in front - speak volumes about their significance. Besides being one of the input devices for the human mind, the eyes also serve as adornments of the human visage - when you look at a person in the face, it is his/her eyes that capture your attention first!

Therefore, with respect to their status as the gems of the human body, the color of the eyes are also a subject of much discussion and admiration. Different people have different eye color preferences, but they have little control over what they themselves are born with. 

The color of the eye is determined by the type and amount of color pigments in the iris of the eye. It is also determined by multiple genes in our chromosomes. The specific genes which play a vital role in determining our natural eye colors include EYCL1 (found on chromosome 19), EYCL2 and EYCL3 (both found on chromosome 15).

Due to the reason that EYCL2 and EYCL3 are found on the same chromosome, they are usually inherited together, though chromosomes sometimes switch genes among themselves under a process known as genetic recombination. EYCL1 is responsible for green/blue eye color while a dominant EYCL2 imparts brown eyes and EYCL3 is responsible for brown/blue eyes.

The variation in combination of these genes lead to varying ratios of the biological color pigment eumelanin that is produced by the melanocytes located in the irises. All three genes have two alleles each (making it a total of 6 alleles) and any combination of these alleles can result in about 8 different eye colors, including some rare combinations.

The eye color of an infant is as much dependent upon racial as upon parental genetics. Here's how the eye color and shade are determined, depending upon how many among the total 6 alleles are dominant -

Pale Blue: 0
Slightly Darker to Deep Blue: 1
Blue-Green: 2
Dark Green to Hazel: 3
Light Brown: 4
Brown-Amber: 5
Dark Brown-Black: 6

Judging from these values, it can be concluded that the more number of dominant alleles you have, the darker your eye color tends to be. Although it is not easy to specifically predict the eye color of a newborn, there are certain hereditary trends that have been studied over years that may help in making close guesses.

For instance, if both parents have light blue eyes, their offspring will not have a darker eye shade. If both parents have somewhat pronounced shades of blue eyes, their child will probably have blue to blue-green eyes but not darker shades like brown or hazel.

Both parents having blue green eyes would most probably have a child with light brown eyes. When both parents are dark brown or black eyed, their issue can have any combination. The same thing can happen if one parent has light brown eyes and the other parent has blue green eyes.

Eye color is not just dependent upon parental heredity, but may be greatly influenced by the genetics and hereditary trends of many preceding generations of the family genealogy. It is not impossible to specifically predict the eye color of a newborn, but that may involve a detailed genetic charting of three-four generations' tendencies.

Mostly, the eye color of a newborn is usually pale to start with and the final color appears by the age of 2 years. People belonging to Asian, African, and Latin ethnicity, however, are usually born with darker eye colors.