In his article, “Blue Eye Color in Humans,” Hans Eiberg writes, “Blue/Brown eye-color are known to the public as a school example of inheritance of monogenetic inheritance, however, the variation in pigment concentration and the iris suggest the eye color genetics to be far more complex as supported by recent data.” In other words, eye color is controlled not by one gene passed from parent to offspring, but by two genes working in tandem a more complex chart would take both of these genes into consideration (Image 2). There are actually two separate genes that control eye color in humans. However, new studies illustrate that the genetics behind eye color are not so straightforward. You have probably seen this explanation accompanied by a simple Punnet square (Image 1) in your science textbooks. The basic explanation of eye-color works like this: a person needs only one dominant brown-eyed gene (from one parent) to be brown-eyed but needs to have two recessive blue-eyed genes (one from each parent) to be blue-eyed. This article will exam the genetic origins of blue eyes in humans, the spread of the blue-eyed gene, and the future of this genetic trait. This discovery helped to confirm theories regarding the familial relationship of nearly all blue-eyed individuals. My interest in this subject was sparked, in part, by a unique archaeological discovery in 2006, researchers uncovered the world's oldest confirmed blue-eyed person, dating to approximately 7,000 years ago. But blue eyes, so popular in art, are relatively new in human evolution, as new as the invention of writing itself. Countless songs and poems reference people with blue eyes, whether considered a mark of beauty, a representation of sadness, or, in certain cultures, a sign of the oppressor. I have blue eyes and I have always been interested in exploring my own genetic origins, but I'm not the only one interested in this genetic trait. These lenses should be worn with the same care as non colored contact lenses.This thoroughly-researched piece is by Sarah Henry, an instructor at Delaware County Community College and tour guide at the Mütter Museum.-KI Many people opt to change or vary their eye color with colored contact lenses. Society has given eye color a lot of emphasis when it comes to appearance and beauty. The genetics, classification and ethnic origins of eye color is a fascinating science. This too can be related to trauma, medications, or a systemic medical condition. Heterochromia is a condition where there is a difference in iris color between two eyes. Yellowing can be associated with jaundice. Some conditions such as melanosis can be benign. The white part of the eye called the conjunctiva and sclera can change color. Eye color can also alert an ophthalmologist to certain medical conditions. People with lighter iris color have a higher prevalence of age-related macular degeneration. There are some medical implications of iris color.
Gray eyes are common in Europe, the Middle East, Afghanistan, and Pakistan.
Green eyes are common in Central Europe, Iraq, Iran and Turkey. About 16 percent of the total world population has blue eyes.īrown eyes are more common in Asia and Europe. Studies have shown that the prevalence of blue eyes in the United States to be approximately 33 percent among Caucasians. Brown eyes have a large concentration of pigment. Blue eyes have a low concentration of pigment in the iris stroma. Interestingly, in blue eyes there is no blue pigment. The color is determined by the concentration of melanin. There is often a mixture of colors from different pigments. Eye color can also be classified by light eyes, mixed eyes, and dark eyes. The colors include amber, blue, brown, gray, green, hazel, red, and violet. There is a very large spectrum of eye color. Eye color can also change during puberty, pregnancy, and after eye trauma. Most eye color changes happen in the first year of life. When a child is born, melanocytes slowly begin to produce melanin. The two main genes are located on Chromosome 15. There could be up to 16 different genes involved in human eye color. Eye color is determined by two distinct factors: pigmentation of the iris and the scattering of light in the stroma of the iris.Įye color is an inherited polygenic trait influenced by many genes. What Determines Your Eye Color? Knowledge Base, April 8, 2016
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