You inherited two recessive blue-eyed genes, one from each parent. This is the key to understanding your blue eyes.
The Genetics of Blue Eyes
Unlike brown eyes, which can be expressed with just one dominant brown-eyed gene from a parent, blue eyes require two recessive genes, one inherited from each parent. As explained in a September 28, 2016, article, "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 genetic inheritance dictates the amount of melanin in your iris. Melanin is the pigment responsible for eye color. Brown eyes have a high amount of melanin, while blue eyes have very little. In fact, according to multiple sources including Verywell Health and All About Vision, blue eyes don't actually have a blue pigment; their appearance is due to the scattering of light in the iris which lacks melanin. This light scattering preferentially reflects blue wavelengths, resulting in the perceived blue color. Auckland Eye concisely summarizes this: "The colour of our eyes depends on how much melanin is present in the iris. Blue eyes get their colour the same way the sky is blue - by the scattering of light."
Several studies have further elucidated the genetics behind blue eyes. Research shows that all blue-eyed individuals share a single common ancestor, a result of a genetic mutation affecting the OCA2 gene, as reported by ScienceDaily and explained in detail on the College of Physicians website. This mutation affects the production of melanin, resulting in the characteristic blue eye color. A non-functioning OCA2 gene, in conjunction with the HERC2 gene's inability to compensate, always leads to blue eyes.
Understanding Melanin's Role
The amount of melanin in your iris directly impacts your eye color. This is why brown eyes are more common than blue eyes. Brown eyes represent the highest concentration of melanin.
- Brown Eyes: High melanin concentration.
- Blue Eyes: Low melanin concentration; the blue color is a result of light scattering.
