Eye color is one of the most distinct features of a person’s appearance. The color of your eyes depends on the amount and quality of melanin in your iris. Melanin is a pigment that gives color to your skin, hair, and eyes. The amount and type of melanin in your body are determined by the genes you inherit from your parents.
The Genetics Behind Eye Color
There are two types of melanin that contribute to eye color:
- Eumelanin – This is a dark brown pigment.
- Pheomelanin – This is a lighter red/yellow pigment.
The OCA2 and HERC2 genes provide instructions for making proteins that are involved in producing melanin. Different versions of these genes result in different amounts of melanin.
Here is how these genes influence eye color:
- Blue eyes have little to no melanin because they have less active versions of OCA2 and HERC2.
- Green or hazel eyes have moderate amounts of melanin.
- Brown eyes have high amounts of melanin.
In addition to these main genes, there are many other genes that impact eye color in subtle ways. This explains why eye colors can range from shades of amber to deep brown.
How Genes Mix to Determine Your Eye Color
Each person inherits one set of genes from their father and one set from their mother. The combination of these genes is what determines your eye color.
Here are some ways that eye color genes can be inherited:
- If both parents have blue eyes, the child will most likely have blue eyes.
- If one parent has brown eyes and one has blue eyes, the child has a 50/50 chance of having brown or blue eyes.
- If one parent has green eyes and one has brown eyes, the child could end up with green, brown, or hazel eyes.
Some genes are dominant and some are recessive. For example, the brown eye trait (high melanin) is generally dominant over the blue eye trait (low melanin). But sometimes blue eyes can be the dominant trait passed down.
How Melanin Levels Change Over Time
While your eye color is primarily determined by genetics, melanin levels can change over your lifetime. Here are some ways that eye color can appear to change:
- Babies are usually born with blue or gray eyes. Eye color can darken over the first few years of life as melanin levels increase.
- Eyes may get darker with age due to melanin clumping together over time.
- The amount of melanin can be affected by health conditions and sun exposure.
- Eyes can also appear to change between shades of green, hazel, amber, gray, and blue depending on lighting conditions, clothes, and surroundings.
Rare and Unique Eye Colors
While brown, blue, and green are the most common eye shades, some people wind up with more unusual colors. Here are some interesting causes of rare eye hues:
- Gray eyes – These tend to occur when small amounts of blue and brown pigment merge in the iris.
- Red/violet eyes – This very rare color is thought to be caused by an unusual distribution of melanin in the iris.
- Heterochromia – Having two different eye colors. Caused by uneven melanin.
- Amber eyes – A solid golden or copper shade. Thought to be a variation of brown eyes.
Certain health conditions like ocular albinism can also cause someone’s eye color to look reddish/violet due to light reflecting off the back of the retina.
Conclusion
In summary, your eye color is determined by the amount of melanin pigment in your iris.
Melanin production is controlled by genetics – primarily the OCA2 and HERC2 genes. The combination of genes you inherit from your parents dictates your eye color.
While genetics are the main factor, eye color can appear to change over time due to aging and sun exposure. Uncommon shades like gray, amber, and red arise from uncommon melanin distributions.
Understanding the scientific factors behind eye color allows you to make sense of how this unique physical trait develops.
| Eye Color | Melanin Level | Gene Variants |
|---|---|---|
| Blue | Low | Less active OCA2 and HERC2 |
| Green | Moderate | Moderate OCA2 and HERC2 |
| Brown | High | Active OCA2 and HERC2 |
