Eye color is a genetically complex human trait, and the genetics of eye color are not as simple as previously thought. Brown eyes were traditionally described as dominant over blue eyes, but this model is overly simplistic. The OCA2 gene is one of the genes that influence eye color, and genetic changes in and around this gene can explain about three-fourths of eye color variation. However, other genes, such as ASIP and IRF4, also help determine eye color.
In terms of dominant and recessive alleles, brown and green alleles are dominant over blue alleles, with brown being the most dominant. If both parents have the dominant brown allele, it is likely that their child will have brown eyes, and the same is true if one parent has a dominant brown allele and the other a recessive blue allele. However, there are many combinations involving dominant and recessive alleles, and its important to keep in mind that combinations of these genes exist and could affect a child's eye color.
It's worth noting that while there is a wide variability in eye color, colors other than brown only exist among individuals of European descent. African and Asian populations are typically brown-eyed.
