Oculocutaneous albinism also affects pigmentation of the iris, but the problem involves the skin and hair as well. In the case of ocular albinism, severely reduced pigmentation of the iris results in very light-colored eyes and vision problems. Several genetic conditions affect the eyes, with two examples being ocular albinism and oculocutaneous albinism. Scientists are still studying exactly how these other factors cause such variations. This is where modifier genes, other genes associated with eye color and mutations all come into picture, as they can all lead to variability in eye color. It also does not explain how grey or hazel eyes arise.
However, this does not explain why two parents with blue eyes can have a child with brown eyes. However, if one of the parents passed on a green allele, then the child would have green eyes and if a brown allele was present, then the child would have brown eyes irrespective of what the other three alleles were. This means parents who happen to have the same eye color can still produce a different eye color in their child.įor example, if two parents with brown eyes each passed on a pair of blue alleles to their offspring, then the child would be born with blue eyes. The allele for brown eyes is the most dominant allele and is always dominant over the other two alleles and the allele for green eyes is always dominant over the allele for blue eyes, which is always recessive. The bey2 gene has one allele for brown eyes and one for blue eyes. The gey gene has one allele that gives rise to green eyes and one allele that gives rise to blue eyes. The different variants of genes are referred to as alleles. The two main gene pairs geneticists have focused on are EYCL1 (also called the gey gene) and EYC元 (also called the bey2 gene). Although a child’s eye color can generally be predicted by looking at the color of the parents’ eyes, the polymorphisms that can arise mean a child may well have an unexpected eye color.Ī child’s eye color depends on the pairing of genes passed on from each parent, which is thought to involve at least three gene pairs. Eye color inheritance patternĭue to the number of genes involved in eye color, the inheritance pattern is complex. The roles of the genes ASIP, IRF4, SLC24A4, SLC24A5, SLC45A2, TPCN2, TYR, and TYRP1 are thought to combine with those of OCA2 and HERC2. At least one polymorphism in this intron reduces the expression and activity of OCA2,which reduces how much P protein is produced.Ī number of other genes play smaller roles in eye color. Intron 86 on this gene controls the expression of OCA2, activating it or deactivating it as required. The other main gene involved is called HERC2.
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