Determinants of Eye Color
Every person is able to carry two copies of each gene. One will be a copy inherited from the father and the other inherited from the mother. When two copies match, or when both copies are for brown eyes, then it is called homozygous.
However, if both copies of the gene are different, or when one is for brown and the other is for non-brown, then this person is heterozygous.
Nevertheless, it is hard to tell just by looking at the eye color of a person, whether he or she is homozygous or heterozygous.
If one copy of the gene is dominant over the other, then the dominant gene exhibits its trait. For instance, a person has one copy of brown-eyed gene, then the other gene copy is hidden.
Brown color is determined by dominant gene, green and hazel by genes which show incomplete dominance. In other words, a brown-eyed person may be able to carry both the brown version and the non-brown version of a particular gene. However, the child may inherit either copy.
When the parents are both brown-eyed, they can have a baby with blue eyes only if both of them are heterozygous. Therefore, if the parents both have blue eyes, then they can’t have a baby with brown eyes. This is because people with blue eyes are only homozygous.
Nevertheless, eye color is polygenic and those other genes can also exert their impact.
Predicting the Eye Color of a Baby
- If both parents have blue eyes, the chance that the baby will have blue eyes is around 99%.
- If the couple has brown eyes, the chance their baby will inherit brown eyes is just 75%. [1]
- If both have green eyes, then the baby will have a 99% chance of having green eyes.
- If both parents have hazel eyes, the baby will have a 99% chance of having hazel eyes.
Hazel eyes are still mysterious, because this can be a mixture of green, brown, and amber hues.
Baby Eye Color Chart When both of the parents have brown eyes
| Heterozygous (More likely) | ||||
|---|---|---|---|---|
| Brown | Blue | Green | Hazel | |
| Brown | 75% brown | 50/50 | 50/50 | 50/50 |
| Blue | 50/50 | 99% blue | 50/50 | 50/50 |
| Green | 50/50 | 50/50 | 99% green | 50/50 |
| Hazel | 50/50 | 50/50 | 50/50 | 99% hazel |
| Homogenous Inheritance (Less Likely) | ||||
|---|---|---|---|---|
| Brown | Blue | Green | Hazel | |
| Brown | 99% brown | 99% brown | 99% brown | 99% brown |
| Blue | 99% brown | 99% blue | 50/50 | 50/50 |
| Green | 99% brown | 50/50 | 99% green | 50/50 |
| Hazel | 99% brown | 50/50 | 50/50 | 99% hazel |
Baby Eye Color Changes
Babies are said to have blue eyes at birth, no matter what the eye color of the parents. Arguably, this is because newborn babies will take more time to produce melanin pigment, which is the dark brown color of the irises of their eyes.
Accordingly, you can’t determine the exact color of the eyes of the baby until she or he turns 3 years old [2].
Progression in the Changes on the Eye Color of the Baby
- At birth, the eye color of babies is light because they don’t have active melanin that will enable it to darken the cells.
- The moment your baby reaches 6 months old, the eye color will begin to change.
- His or her eye color will gradually take on a different shade based on genetic inheritance. This change will begin to happen after 6 months.
- By the time he or she reaches 3 years old, your baby will have a definite eye color. By this time, it will no longer change further.
- As most Asian and African babies are being born with brown eye color, Caucasian babies may have blue or gray eyes. This will change as they grow older.
The Waardenburg Syndrome
In rare cases, babies are born with 1 brown eye and 1 blue. This is due to a medical condition called the Waardenburg Syndrome. This is a rare genetic disorder and it is essential to consult an ophthalmologist. Nevertheless, studies are still being conducted to find the accurate reasons behind the eye color changes in newborns.
Personality Traits behind Each Eye Color
- Green – people with green eye color are considered enigmatic and mysterious. These types of people have an incredible zeal and zest for life.
- Brown – this is the most dominant eye color worldwide. Those with brown eyes are mostly very positive, attractive, and confident.
- Hazel – those with hazel eyes are referred to as elegant beings. They are always up for adventure, and are fun loving and spontaneous.
- Blue – this is the most desired eye color worldwide. Those with blue eyes are willing to go the extra mile to ensure that everybody is happy with them.
Science behind the Inheritance of Eye Color
Arguments regarding eye color being passed from parent to offspring have been around for decades as a topic for debate among geneticists. It has been thought that eye color will follow the simple pattern of the Mendelian inheritance.
According to the Mendelian inheritance rules, eye color will be inherited similarly to the way hair color is inherited. Thus, genes for darker colors will be dominant, which means the phenotypes or traits they code for will take precedence over the traits being coded for a lighter color by genes.
Nowadays, though, there are lots of online eye color calculators you can use to predict and calculate the resulting eye color of your baby.
References
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1. https://www.babymed.com/tools/baby-eye-color-calculator-predictor?p1=Brown&p2=Brown
2. http://mentalfloss.com/article/73016/why-do-babies-eyes-change-color
