Is eye color determined by genetics?: MedlinePlus Genetics (2024)

A person’s eye color results from pigmentation of a structure called the iris, which surrounds the small black hole in the center of the eye (the pupil) and helps control how much light can enter the eye. The color of the iris ranges on a continuum from very light blue to dark brown. Most of the time eye color is categorized as blue, green/hazel, or brown. Brown is the most frequent eye color worldwide.

Eye color is determined by variations in a person’s genes. Most of the genes associated with eye color are involved in the production, transport, or storage of a pigment called melanin. Eye color is directly related to the amount of melanin in the front layers of the iris. People with brown eyes have a large amount of melanin in the iris, while people with blue eyes have much less of this pigment.

A particular region on chromosome 15 plays a major role in eye color. Within this region, there are two genes located very close together: OCA2 and HERC2. The protein produced from the OCA2 gene, known as the P protein, is involved in the maturation of melanosomes, which are cellular structures that produce and store melanin. The P protein therefore plays a crucial role in the amount and quality of melanin that is present in the iris. Several common variations (polymorphisms) in the OCA2gene reduce the amount of functional P protein that is produced. Less P protein means that less melanin is present in the iris, leading to blue eyes instead of brown in people with a polymorphism in this gene.

A region of the nearby HERC2gene known as intron 86 contains a segment of DNA that controls the activity (expression) of the OCA2gene, turning it on or off as needed. At least one polymorphism in this area of the HERC2gene has been shown to reduce the expression of OCA2 and decrease P protein production, leading to less melanin in the iris and lighter-colored eyes.

Several other genes play smaller roles in determining eye color. Some of these genes are also involved in skin and hair coloring. Genes with reported roles in eye color include ASIP, IRF4, SLC24A4, SLC24A5, SLC45A2, TPCN2, TYR, and TYRP1. The effects of these genes likely combine with those of OCA2and HERC2to produce a continuum of eye colors in different people.

Researchers used to think that eye color was determined by a single gene and followed a simple inheritance pattern in which brown eyes were dominant to blue eyes. Under this model, it was believed that parents who both had blue eyes could not have a child with brown eyes. However, later studies showed that this model was too simplistic. Although it is uncommon, parents with blue eyes can have children with brown eyes. The inheritance of eye color is more complex than originally suspected because multiple genes are involved. While a child’s eye color can often be predicted by the eye colors of his or her parents and other relatives, genetic variations sometimes produce unexpected results.

Several disorders that affect eye color have been described. Ocular albinism is characterized by severely reduced pigmentation of the iris, which causes very light-colored eyes and significant problems with vision. Another condition called oculocutaneous albinism affects the pigmentation of the skin and hair in addition to the eyes. Affected individuals tend to have very light-colored irises, fair skin, and white or light-colored hair. Both ocular albinism and oculocutaneous albinism result from mutations in genes involved in the production and storage of melanin. Another condition called heterochromia is characterized by different-colored eyes in the same individual. Heterochromia can be caused by genetic changes or by a problem during eye development, or it can be acquired as a result of a disease or injury to the eye.

Eye anatomy

Is eye color determined by genetics?: MedlinePlus Genetics (1)

Scientific journal articles for further reading

Sturm RA, Duffy DL, Zhao ZZ, Leite FP, Stark MS, Hayward NK, Martin NG, Montgomery GW. A single SNP in an evolutionary conserved region within intron 86 of the HERC2 gene determines human blue-brown eye color. Am J Hum Genet. 2008 Feb;82(2):424-31. doi: 10.1016/j.ajhg.2007.11.005. Epub 2008 Jan 24. PubMed: 18252222. Free full-text available from PubMed Central: PMC2427173.

Sturm RA, Larsson M. Genetics of human iris colour and patterns. Pigment Cell Melanoma Res. 2009 Oct;22(5):544-62. doi: 10.1111/j.1755-148X.2009.00606.x. Epub 2009 Jul 8. Review. PubMed: 19619260.

White D, Rabago-Smith M. Genotype-phenotype associations and human eye color. J Hum Genet. 2011 Jan;56(1):5-7. doi: 10.1038/jhg.2010.126. Epub 2010 Oct 14. Review. PubMed: 20944644

Is eye color determined by genetics?: MedlinePlus Genetics (2024)


Is eye color determined by genetics?: MedlinePlus Genetics? ›

Genetics is the study of heredity, the process of a parent passing certain genes to their children. A person's appearance -- height, hair color, skin color, and eye color -- is determined by genes.

Is eye color determined by genetics? ›

The inheritance of eye color is more complex than originally suspected because multiple genes are involved. While a child's eye color can often be predicted by the eye colors of his or her parents and other relatives, genetic variations sometimes produce unexpected results.

How your DNA determines the color of your eyes and hair? ›

DNA contains all the information needed to build your body. Did you know that your DNA determines things such as your eye color, hair color, height, and even the size of your nose? The DNA in your cells is responsible for these physical attributes as well as many others that you will soon see.

Does eye color have anything to do with ancestry? ›

Eye color is not as cut and dry as we once believed, but an offspring can inherit virtually any eye color no matter how rare. Your eyes can say a lot about your ancestral lineage because of the complex genetic coding that is involved with eye color, and here is a closer look into what your eye color means…

What is the dominant gene for eye color? ›

Eye colour, or more correctly iris colour, is often used as an example for teaching Mendelian genetics, with brown being dominant and blue being recessive.

What color is the rarest eye color? ›

Gray: The Rarest Eye Color

With this change, gray now tops the list as the rarest eye color. Gray eyes may contain just enough melanin in the front layer to dim the blue wavelengths of light that are reflected back by the tissue of the eye. Dark gray eyes have a bit more melanin in the front layer than pale gray eyes.

Can two brown eyes make blue? ›

Flexi Says: Two brown-eyed parents (if both are heterozygous) can have a blue-eyed baby. If both the parents have brown eyes, then there is generally a 25% chance for their child to have blue eyes. Because both the brown-eyed parents have a recessive blue-eye gene and can pass it to the next generation.

Can you tell someone's eye color from their DNA? ›

In turn, your eye color likely reflects the variant you have. Thus, your DNA can tell you whether you may have brown eyes (a dominant trait) or blue eyes (a recessive trait).

What determines what color of hair or eyes you have? ›

The color of our hair, skin, and eyes is determined by the same thing: the amount of pigment they have. The pigment that causes dark hair, skin, and eyes is called melanin. Melanin is made in special cells in the body called melanocytes.

What is the role of DNA in determining traits like eye color? ›

Answer and Explanation:

DNA can determine traits such as eye color because it has the ability to control certain observable features called phenotypes. Think of a person's hair color, eye color, height, and even behavior. These are all features that can be observed. In genetics, these features are called phenotypes.

What color eyes did Vikings have? ›

Yes, the ancient Norsem*n of the Viking Age were commonly known to have blue eyes. This distinct physical trait is often associated with the Scandinavian region and its historical inhabitants.

What ancestry has GREY eyes? ›

This rare eye colour is most common among people of European descent, especially those born in countries like Norway, Iceland, Sweden, Ireland and Finland. In Asia and Africa, it is one of the rarest eye colours.

Which race has hazel eyes? ›

Anyone can be born with hazel eyes, but it's most common in people of Brazilian, Middle Eastern, North African, or Spanish descent. When eyes are hazel, they are brown mixed with amber and green. In some cases, there are shades of gray, blue, and gold within the iris too.

What is the prettiest eye color? ›

When broken down by gender, men ranked gray, blue, and green eyes as the most attractive, while women said they were most attracted to green, hazel, and gray eyes. Despite brown eyes ranking at the bottom of our perceived attraction scale, approximately 79% of the world's population sports melanin-rich brown eyes.

What eye color is the strongest gene? ›

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.

Who determines eye color in genetics? ›

The amount of melanin in the iris is determined by several genes, including the OCA2 gene mentioned earlier. Other genes, such as TYR and SLC24A4, also play a role in melanin production. Interestingly, the same genes that determine melanin production in the skin and hair also play a role in eye color determination.

Which parents determines eye color? ›

While a baby inherits half of their eye color genetics from one parent and half from the other parent, the way that the multiple genes interact also plays a role in determining eye color.

What determines the color of your eyes? ›

There are two main factors that help determine your eye color: the amount and pattern of dark brown pigment (called melanin) in the part of your eye called the iris and the way in which the iris scatters light that passes through the eye. The more important factor is pigment, which is determined by your genes.

Is your eye color determined by your brothers or sisters? ›

Eye color is determined by genetics and genes can vary between siblings. We all have genes in our body, and our genes carry DNA. Our DNA controls the way that we express different characteristics in our body, everything from hair color to eye color to skin color.

Why are green eyes so rare? ›

Why Are Green Eyes So Rare? The chance of being born with green eyes hinges on a "complex interplay" of multiple genes and single nucleotide polymorphisms (SNPs), "making precise prediction challenging," Sexton noted.


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