When two genes combine in a certain way that produce no eye-color pigment, blue eyes occur. These two genes located in chromosome 15, HERC2 and OCA2, specifically determine eye color. The genetic information passes from parents to offspring; half the chromosomes come from the mother and half from the father.Continue Reading
An individual requires working HERC2 and OCA2 genes to be born with brown eyes. If someone has a broken HERC2 or OCA2 gene, the individual is born with blue eyes, because the two genes need each other to make pigment found in brown eyes. Brown eyes have pigment, but blue eyes do not.
Research suggests that all humans with blue eyes have a single common ancestor. Scientists found a genetic mutation that happened 6,000 to 10,000 years ago with the OCA2 gene, and it is the cause of all blue eyes in humans today.Learn more about Biology