The Genetics of Hazel Eyes: The Enigma of Eye Color Variation

kilala Apr 19, 2023

Eye color has always been a topic of fascination for both scientists and the general public alike. Hazel eyes, in particular, stand out as an intriguing and enchanting shade, often described as a unique blend of green, brown, and gold.

In this blog post, we'll delve into the genetics of hazel eyes, how they differ from other eye colors, and the complex interplay between various genetic factors that result in this captivating color.

Unraveling the Genetics of Hazel Eyes


Unlike the more common eye colors like blue, brown, and green, hazel eyes are not determined by a single gene or a straightforward genetic pathway. Instead, the hazel eye color is the result of a complex interplay between various genes that regulate melanin production and distribution in the iris.

Researchers believe that the hazel eye color arises from a combination of factors such as:

  • A moderate amount of melanin in the front part of the iris results in a greenish hue.
  • A higher concentration of melanin in the back part of the iris gives a brownish appearance.
  • A higher proportion of pheomelanin, which imparts a golden or amber hue.

The intricate balance between these factors creates the unique and striking appearance of hazel eyes, setting them apart from other eye colors.

Hazel Eyes vs. Other Eye Colors

Hazel eyes exhibit noticeable differences when compared to other eye colors, both in appearance and genetics. Here's a brief comparison:

  • Blue Eyes: Blue eyes have a low concentration of melanin in the front part of the iris, which allows the scattering of light to create a blue hue. A specific mutation in the HERC2 gene, which turns off the OCA2 gene, results in blue eyes. Hazel eyes, on the other hand, have a higher melanin concentration, leading to their distinct coloration.
  • Brown Eyes: Brown eyes have a high concentration of melanin in the iris, primarily eumelanin, which creates a brown color. Although both brown and hazel eyes have melanin, the difference in their distribution and the presence of pheomelanin in hazel eyes create a distinct appearance.
  • Green Eyes: Green eyes result from a moderate amount of melanin in the iris, combined with the scattering of light. While hazel eyes share some similarities with green eyes, the presence of pheomelanin and the pattern of melanin distribution make hazel eyes unique.


The Enigma of Eye Color Inheritance

Eye color inheritance is not as simple as once believed. While early genetic models proposed that eye color was determined by a single gene with two alleles (one for brown and one for blue), we now know that eye color is a polygenic trait, meaning it is influenced by multiple genes.

Given the complexity of eye color genetics, predicting a child's eye color based on the parents' eye color is far from straightforward. For instance, two brown-eyed parents may have a child with hazel eyes, while two blue-eyed parents might have a child with green eyes.

This is because each parent carries multiple genes that can influence eye color, and the specific combination of these genes inherited by the child will determine their eye color.


The genetics of hazel eyes is a fascinating subject, reflecting the intricate and complex nature of human biology. The interplay between multiple genes and factors, as well as the unique appearance of hazel eyes, sets them apart from other eye colors.

As our understanding of genetics continues to advance, we will undoubtedly uncover more about the specific genes and mechanisms that determine eye color, including the captivating hazel shade.

Until then, the enigma of hazel eyes will continue to intrigue both scientists and laypeople alike, serving as a reminder of the wonders of human diversity and the beauty of our individual characteristics.

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