Brown eyes are the most common eye color worldwide, and they are the result of a combination of genetic factors. The pigment responsible for brown eyes is called melanin, which is also responsible for skin and hair color.
How Melanin Determines Eye Color
- More Melanin = Darker Eyes: The more melanin present in the iris, the darker the eye color will be. Brown eyes have a high concentration of melanin in the iris.
- Less Melanin = Lighter Eyes: Lighter eye colors, like blue or green, have less melanin in the iris.
The Genetics of Eye Color
Eye color is a complex trait determined by multiple genes. However, one gene, called the OCA2 gene, plays a significant role in determining eye color. This gene produces a protein called P protein, which is involved in the production of melanin.
- Variations in the OCA2 gene: Different variations, or alleles, of the OCA2 gene exist. Some alleles produce more P protein, leading to more melanin and darker eye colors. Other alleles produce less P protein, resulting in less melanin and lighter eye colors.
- Inheritance: People inherit two copies of the OCA2 gene, one from each parent. The combination of these alleles determines the eye color of the individual.
Why Brown Eyes are Dominant
Brown eyes are considered dominant over other eye colors, meaning that if someone inherits at least one copy of the brown eye allele, they will have brown eyes. To have a lighter eye color, like blue or green, a person must inherit two copies of the lighter eye color alleles.
Conclusion
Brown eyes are a result of a high concentration of melanin in the iris, which is determined by the genes we inherit from our parents. The OCA2 gene plays a significant role in melanin production, and the variations in this gene influence the color of our eyes. Brown eyes are dominant over other eye colors, meaning that even if someone inherits one copy of the brown eye allele, they will have brown eyes.
