The Gene That Causes a Change in Pigment
The OCA2 gene codes for the production of the P protein, which plays a crucial role in melanin production and determining skin color. The mutation in the adjacent gene to OCA2 regulates the action of the P protein, reducing the production of melanin in the iris and diluting the brown color to a shade of blue. This specific mutation is present in all blue-eyed individuals today, indicating that they are linked to the same ancestor.