The primary gene responsible for eye color is OCA2.
Here's a more detailed explanation:
Eye color is a complex trait determined by multiple genes. While other genes play a role, OCA2 is considered the major player. Located on chromosome 15, OCA2 encodes a protein that helps regulate the production and distribution of melanin, the pigment responsible for the varying shades of brown in our eyes (and skin and hair).
How OCA2 Works:
- Melanin Production: The OCA2 protein controls the amount of melanin produced in the iris.
- Variations in the Gene: Different variations (alleles) of the OCA2 gene lead to different levels of melanin production.
- Eye Color Outcomes:
- High Melanin: Brown eyes
- Moderate Melanin: Hazel or green eyes
- Low Melanin: Blue eyes
Other Genes Involved:
While OCA2 is the primary gene, other genes also contribute to eye color, including:
- HERC2: This gene regulates the expression of OCA2. A variation in HERC2 can switch off OCA2, leading to reduced melanin production and blue eyes.
- EYCL1 (also known as GEY): Plays a role in green/blue eye color.
- EYCL2: Plays a role in brown eye color.
- EYCL3: Plays a role in blue eye color.
Importance of Understanding the Genetics of Eye Color:
Understanding the genetic basis of eye color provides insights into:
- Human Genetics: Understanding how genes interact to determine complex traits.
- Evolution: Studying the evolution and distribution of different eye colors across populations.
In summary, while multiple genes contribute, the OCA2 gene is the primary determinant of eye color, controlling melanin production in the iris. Variations in this gene, often in combination with variations in other genes like HERC2, lead to the spectrum of eye colors we see.
