Is Eye Color Genetic?

Pigments Behind Your Eye Color

People have varying eye colors and shades– from dark to light brown, green, hazel, black, gray, and blue.?

A few people have different colors in both their eyes.

Despite these varying eye colors, you will be surprised to know that?there are just two pigments in our eyes?- brown and red.

The colored part of the eye is called the iris. The iris contains pigment-forming cells called melanocytes, the same ones present?in our?skin.

These?melanocytes produce two pigments?–?eumelanin?(which is brown-black) and pheomelanin (which is red).

The varying shades of eye color depend upon the amount of pigment produced.

For example, people with dark eye color have a large amount of brown-black eumelanin, whereas those with light blue eyes have very little pigment.

Image: Is Eye Color Genetic: Types of Melanin Pigment

Is Eye Color Genetic? - The?OCA2?and?HERC2?Genes

Just like fingerprints, eye color is unique to an individual and is genetically determined.?

A?genome-wide association study?identified 115 genetic variants associated with eye color.

Two genes located close to each other on chromosome 15–?OCA2?and?HERC2?are said to play an important role in eye color determination.

Though?the OAC2 gene influences 75% of eye color, other genes also play a role in melanin production.

The?OAC2?gene gives instructions to produce the P protein that helps in the maturation of melanosomes (cellular structures that make and store melanin).

The P protein influences the amount of melanin in the iris.

Common changes (called variations or polymorphisms) in the?OAC2?gene may reduce the amount of P protein produced.?

People with less P protein have less melanin in their eyes.?

This also means they may have blue eyes instead of brown.

The?HERC2?gene is located very close to the?OAC2?gene.?

A part of the?HERC2?gene is also called intron 86. This region regulates the activity of the?OAC2?gene.

At least one polymorphism in the?HERC2?gene area has been shown to?reduce the?OAC2?gene and decrease P protein production.?

This results in less melanin in the iris and light-colored eyes.

Inheritance of Eye Color

Though eye color is genetically determined, it?is also an inherited trait.

For a long, scientists believed that a single gene was responsible for an individual’s eye color. However, the inheritance of eye color is far more complex.

The study of?inheritance and genetics of eye color is still in the nascent stages.

Image: Is Eye Color Genetic: Inheritance of Eye Color

Source:?https://www.nature.com/articles/s41433-021-01749-x

Can Eye Color Be Predicted?

It is impossible to predict a baby's eye color with 100% certainty.?

But with certain genetic rules, it is possible to make a fair guess.

For example, the brown eye is a?dominant trait?- this means it can hide traits of green and blue eyes.

To find the possibility of recessive traits, it's helpful to know the grandparents' eye colors.

For example, if the mother has blue eyes and her entire family has blue eyes and the father has brown eyes with his mother and father with brown and blue eyes, the kid will have a 50/50 chance of having a blue-eyed or brown-eyed child.

Source:?https://www.verywellhealth.com/genetics-of-eye-color-3421603

Summary

1. Melanocytes produce two types of pigments in the eye – eumelanin (brown-black) and pheomelanin (red).
2. The greater the amount of pigment, the darker the eye color.
3. Two genes –?OAC2?and?HERC2, play a vital role in eye color determination.
4. The?OAC2?gene determines 75% of eye color, while other genes influence the rest.
5. Eye color inheritance is complex as several genes are involved.
6. Though parents' eye color can help determine that of the child, some variations may cause unexpected results.

References

• https://medlineplus.gov/genetics/understanding/traits/eyecolor/
• https://www.verywellhealth.com/genetics-of-eye-color-3421603
• https://www.gbhealthwatch.com/Trait-Eye-Color.php

First appeared in https://www.xcode.life/genetic-traits/is-eye-color-genetic/