How Are Blue Eyes Inherited?
- Pieter Maas
Before you request a paternity test, spend a few minutes looking at your child’s eye color. It may just give you the answer you’re looking for. According to Bruno Laeng and colleagues, from the University of Tromso, Norway, the human eye color reflects a simple, predictable and reliable genetic pattern of inheritance.
- Their studies 1, published in the Springer journal Behavioral Ecology and Sociobiology, show that blue-eyed men find blue-eyed women more attractive than brown-eyed women.
- According to the researchers, it is because there could be an unconscious male adaptation for the detection of paternity, based on eye color.
The laws of genetics state that eye color is inherited as follows:
If both parents have blue eyes, the children will have blue eyes. The brown eye form of the eye color gene (or allele) is dominant, whereas the blue eye allele is recessive. If both parents have brown eyes yet carry the allele for blue eyes, a quarter of the children will have blue eyes, and three quarters will have brown eyes.
It then follows that if a child born to two blue-eyed parents does not have blue eyes, then the blue-eyed father is not the biological father. It is therefore reasonable to expect that a man would be more attracted towards a woman displaying a trait that increases his paternal confidence, and the likelihood that he could uncover his partner’s sexual infidelity.
Eighty-eight male and female students were asked to rate facial attractiveness of models on a computer. The pictures were close-ups of young adult faces, unfamiliar to the participants. The eye color of each model was manipulated, so that for each model’s face two versions were shown, one with the natural eye color (blue/brown) and another with the other color (brown/blue).
The participants’ own eye color was noted. Both blue-eyed and brown-eyed women showed no difference in their preferences for male models of either eye color. Similarly, brown-eyed men showed no preference for either blue-eyed or brown-eyed female models.
- However, blue-eyed men rated blue-eyed female models as more attractive than brown-eyed models.
- In a second study, a group of 443 young adults of both sexes and different eye colors were asked to report the eye color of their romantic partners.
- Blue-eyed men were the group with the largest proportion of partners of the same eye color.
According to Bruno Laeng and colleagues, “It is remarkable that blue-eyed men showed such a clear preference for women with the same eye color, given that the present experiment did not request participants to choose prospective sexual mates, but only to provide their aesthetic or attractiveness responsesbased on face close-up photographs.” Blue-eyed men may have unconsciously learned to value a physical trait that can facilitate recognition of own kin.1.
Can you inherit blue eyes from grandparents?
What color eyes will my child have? – There’s no guarantee when it comes to your offspring’s 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 genes interact also plays a role in determining eye color.
- Differences in eye color are also influenced by differing amounts of melanin, the pigment responsible for eye color (plus hair color and skin tone).
- For instance, many white non-Hispanic babies are born with blue eyes because they don’t have the full amount of melanin present in their irises at birth.
As the child grows older, if they’ve developed slightly more melanin in their irises, the eyes will be green or hazel, When the iris stores a lot of melanin, the eyes will be amber (a golden brown), light brown or dark brown. Even though you don’t know the amount of melanin your baby will have, you can still get a pretty good sense of eye color from the parents’ eye colors.
Two blue-eyed parents are likely to have a blue-eyed child, but it’s not guaranteed. Two brown-eyed parents are likely to have a brown-eyed child. Again, it’s not guaranteed. Two green-eyed parents are likely to have a green-eyed child, although there are exceptions. Two hazel-eyed parents are likely to have a hazel-eyed child, although a different eye color could emerge. If one of the grandparents has blue eyes, the odds of having a baby with blue eyes increases slightly. If one parent has brown eyes and the other has blue eyes, the chances of having a brown-eyed or blue-eyed baby are roughly even.
The Fertility Institutes, which offers fertility services in California, New York, Utah and Mexico, offers the following odds of a baby’s eye color based on the parents’ eye colors. (Due to rounding, percentages don’t always add up to 100%.)
Both parents with brown eyes: 75% chance of baby with brown eyes, 18.8% chance of baby with green eyes, 6.3% chance of baby with blue eyes. Both parents with blue eyes: 99% chance of baby with blue eyes, 1% chance of baby with green eyes, 0% chance of baby with brown eyes. Both parents with green eyes: 75% chance of baby with green eyes, 25% of baby with blue eyes, 0% chance of baby with brown eyes. One parent with brown eyes and one parent with blue eyes: 50% chance of baby with brown eyes, 50% chance of baby with blue eyes, 0% chance of baby with green eyes. One parent with brown eyes and one parent with green eyes: 50% chance of baby with brown eyes, 37.5% chance of baby with green eyes, 12.5% chance of baby with blue eyes. One parent with blue eyes and one parent with green eyes: 50% of chance of baby with blue eyes, 50% chance of baby with green eyes, 0% chance of baby with brown eyes.
Keep in mind that it may take six to 12 months for a baby’s true eye color to emerge, so the color you see at birth can certainly change. SEE RELATED: Is it true all babies are born with blue eyes?
Who does the blue eye gene come from?
Blog 1. Only 8 Percent of the World’s Population Has Blue Eyes If you have got blue eyes, you might just belong to one of the world’s most exclusive groups without realising it! Since blue eyes are genetically recessive, only 8 percent of the world’s population has blue eyes.
While blue eyes are significantly less common than brown eyes worldwide, they are frequently found from nationalities located near the Baltic Sea in northern Europe.2. There is No Blue Pigment in Blue Irises The colour of our eyes depends on how much melanin is present in the iris. Blue eyes get their colour the same way water and the sky get their blue colour — they scatter light so that more blue light reflects back out.
The iris is made up of two layers. For almost everyone — even people with blue eyes — the back layer (called the pigment epithelium) has brown pigment in it. The front layer of the iris (called the stroma) is made up of overlapping fibers and cells. For people with brown eyes, some of the cells also have brown pigment in them.
- If there is no pigment at all in this front layer, the fibers scatter and absorb some of the longer wavelengths of light that come in.
- More blue light gets back out and the eyes appear to be blue.3.
- Blue Eyes are More Sensitive to Light Melanin in the iris of the eye appears to help protect the back of the eye from damage caused by UV radiation and high-energy visible “blue” light from sunlight and artificial sources of these rays.
Since blue eyes contain less melanin than green, hazel or brown eyes, photophobia is more prevalent in blue eyes compared to darker coloured eyes. For these reasons, having less melanin in your irises means that you need to protect your eyes more from the sun’s UV rays.
- Therefore, it is recommended to those with blue eyes to stay out of the sun for long periods of time and try to wear protective eyewear when you are outdoors.4.
- All Blue-Eyed People May Have A Common Ancestor Originally we all had brown eyes, however, according to researchers at the University of Copenhagen, it appears that a genetic mutation in a single individual in Europe 6,000 to 10,000 years ago led to the development of blue eyes.
Therefore, we can conclude that this genetic mutation is the cause of eye colour of all blue-eyed humans alive on the planet today. What is the genetic mutation? A genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a “switch”, which “turned off” the ability to produce brown eyes.
- The OCA2 gene codes for the ‘P protein’, which is involved in the production of melanin (the pigment that determines the colour of our eyes, skin and hair).
- The “switch”, does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris – effectively “diluting” brown eyes to blue.
According to Hans Eiberg, associate professor in the Department of Cellular and Molecular Medicine from the University of Copenhagen, “From this, we can conclude that all blue-eyed individuals are linked to the same ancestor. They have all inherited the same switch at exactly the same spot in their DNA.” 5.
Blue Eyes at Birth Doesn’t Mean Blue Eyes For Life While blue eyes may be rare, they’re among the most common eye colours at birth. Since the human eye does not have its full adult amount of pigment at birth, most Caucasian babies are born with blue eyes. However, since human melanin tends to develop over time — this causes the child’s eye colour to change as more melanin is produced in the iris during early childhood.6.
People With Blue Eyes May Have a Higher Risk of Alcoholism A new study suggests that individuals with blue eyes are at a higher risk for alcohol dependency compared to those with darker eyes. Therefore, this finding adds further evidence to the idea that alcoholism has a genetic component.
A study published in American Journal of Medical Genetics, Part B: Neuropsychiatric Genetics found that European Americans with blue eyes had up to 83 percent higher odds of becoming dependent on alcohol, compared with matched controls who had darker eye colours. This research suggests that alcoholism has a genetic component linked to genetic sequences that determine eye colour, which may help explain the association.
However, at this stage, the reason for the correlation is still unknown and further research is required to fully understand this correlation in the findings.7. You Can’t Predict the Colour of Your Child’s Eyes Since it was once believed that eye colour — including blue eyes — was a simple genetic trait, many people used to believe that blue-eyed people could only have blue-eyed children.
Before geneticists fully understood how human eye colour inheritance works, a child’s eye colour to used be used as a paternity test — based on the assumption that you could predict a child’s eye colour if you knew the colour of the parents’ eyes and perhaps the colour of the grandparents’ eyes. But geneticists now know that this concept is far more complicated, as eye colour is influenced by an interaction of as many as 16 different genes — not just one or two genes as once thought.
Additionally, the anatomic structure of the iris can also influence eye colour to some degree. In summary, it’s impossible to know for sure if your children will have blue eyes. Even if you and your partner both have blue eyes, that’s no guarantee your child’s eyes will also be blue.
Can a baby have blue eyes if both parents have green?
How is it possible that I have blue eyes when my father has brown and my mother green? Editor’s note (1/25/2021): This article describes a two-gene model for eye color. While this was a standard model for years, it is over simplified. Eye color is a complex trait influenced by at least a dozen different genes.
- That makes it harder to predict, with much more complicated genotypes, than described here.
- You’re right.
- If there was just one eye color gene, then your situation would be pretty uncommon.
- And yet your situation can and does happen. A lot.
- A brown eyed dad and a green eyed mom can have a blue eyed child because there are at least two eye color genes.
Because of this, it is possible for both green and brown eyed parents to be carriers for blue eyes. And as carriers, they each can pass down blue eye genes to their children. Let’s go into a bit more detail about how all of this works. We’ll also do Punnett squares for the two most likely possibilities in your case to figure out the chances of your parents having a blue eyed child.
The first thing to notice from this table is that whenever there is a B, there are brown eyes. So B is dominant over both G and b. Also, whenever there is a G (but no B), there are green eyes. So G is dominant over b. A couple of things might seem weird here.
- First, there are two separate genes and yet B from one gene is dominant over G from another gene.
- Eye color happens because of the amount of the pigment melanin found in the eye.
- Not anywhere in the eye but in a very special place, the stroma of the iris.
- Lots of melanin here gives brown eyes and less melanin gives green.
Little or no melanin in the stroma of the iris gives blue eyes. So this is why brown is dominant over green. The B version of OCA2 tells the eye to make lots of melanin. The G version of the gey gene tells the eye to make some. What happens if both are present? Lots of melanin gets made which means brown eyes.
- The fact that both recessive forms are blue makes sense from this as well.
- The recessive forms of these two genes are recessive because they don’t work.
- A broken OCA2 gene is the same as a broken gey gene-no melanin gets made in the stroma.
- No melanin in the stroma means blue eyes.
- OK, so now we see why brown is dominant over green.
And why blue is recessive to both. But we still haven’t explained your situation. We can figure this out from noting something else in the table-all the eye colors have two versions of each gene. There are two copies of OCA2 and two copies of gey in each case.
- This is because we have two copies of most of our genes, one from mom and one from dad.
- It is this fact that allows for a brown eyed dad and a green eyed mom to have a blue eyed child.
- Let’s look at OCA2 as an example.
- If someone has two B versions, then obviously they have brown eyes.
- And if they have two b versions, then they don’t have brown eyes (they’ll have either green or blue).
But what if they have one B and one b? Then they have brown eyes. But half of the time they will pass the blue version to their kids. And if the other parent passes the b version of OCA2 as well, then the child will not have brown eyes. This all works for the gey gene too.
- So in your case, the easiest way to explain your blue eyes is if both your mom and dad are carriers for blue eyes.
- Your mom is most likely bb Gb and your dad is either Bb Gb or Bb bb (we can’t tell the difference).
- These are written as the first pair of letters from OCA2 (the brown-blue gene) and the second pair from gey (the green-blue gene).
So each parent gave a b from OCA2 and a b from gey. The end result is that you are bb bb which is blue eyes. Let’s figure out how likely it was for you to end up with blue eyes. To do this, we’ll set up two Punnett squares, one for each of your dad’s possibilities.
The way a Punnett square works is you make a table. We’ll do an easy one first with just OCA2 (the brown or blue eye gene). The first step is to put your dad’s two possible gene versions on the top like this: Since we are saying your dad is a brown-eyed carrier of blue eyes, he has a B (brown) and a b (blue) version of OCA2.
The next step is to put your mom’s gene versions on the side of the table like this: As you can see, in this example, I put your dad’s brown eyes on top (Bb) and your mom’s blue eyes (bb) on the side. Remember, your dad and mom only contribute one version of OCA2 each.
- Your dad can give either a B or a b, not both.
- The Punnett square gives you all four possibilities of your dad and mom’s combinations.
- The next step is to fill in each square with the letters from the top or side to figure out what is possible.
- For example, in the first square, since there is a B from your dad and a b from your mom, a Bb goes in like this: This represents a brown eyed carrier of blue eyes.
You then fill in the rest of the square like this: From this, you can figure out that your parents had a 50-50 shot of having brown-eyed kids (Bb). Note that all the brown eyed kids will be carriers for the blue eyed version of the gene, b. Now, to add the green gene, it gets more complicated.
Each of the two genes is independent of each other so you need to figure out all of the possibilities your parents could have. Your mom will be bb Gb. Your dad could be either Bb Gb or Bb bb. If your dad is Bb Gb, then the square will look like this: You do the same thing as before and combine the boxes.
The first box would be Bb GG, a brown-eyed carrier of green eyes. If we fill in all of the possibilities, we get:
|bG||Bb GG||Bb Gb||bb GG||bb Gb|
|bb||Bb Gb||Bb bb||bb Gb||bb bb|
|bG||Bb GG||Bb Gb||bb GG||bb Gb|
|bb||Bb Gb||Bb bb||bb Gb||bb bb|
From this, we can figure that if your dad was a carrier for green eyes, then your parents had a 2 in 16 (or 1 in 8) chance of having a blue eyed child. If instead your dad is Bb bb, then the Punnett square would look like this:
|bG||Bb Gb||Bb Gb||bb Gb||bb Gb|
|bb||Bb Gb||Bb bb||bb bb||bb bb|
|bG||Bb Gb||Bb Gb||bb Gb||bb Gb|
|bb||Bb Gb||Bb bb||bb bb||bb bb|
In this case, each child of your parents has a 4 in 16 (or 1 in 4) chance for blue eyes. So there you have it. Sorry it was so long but now you know how it is possible for a brown eyed dad and a green eyed mom to have a blue eyed child. And the odds of it happening. : How is it possible that I have blue eyes when my father has brown and my mother green?
What are the chances of a blue-eyed baby with brown-eyed parents?
Brown eye colour is dominant over blue eye colour. Therefore, for the brown-eyed parents having blue-eyed child, the possibility is that both have heterozygous genotype i.e. Bb. Therefore, from the square below, it is clear that there is a 25% possibility of blue-eyed (bb) child.
Can a brown-eyed and a blue-eyed person have a blue-eyed child?
Making Eye Color Predictions with Basic Genetics – If you want to try and predict your baby’s eye color, pull out your high school biology textbook to help narrow down just how likely it is that your baby will have blue eyes. If you didn’t keep it, don’t worry, I’ll give you a quick review.
- As FamilyEducation’s Genetics Expert, I have developed my knowledge on these topics through a combination of college classes, teaching, and self-study.
- We all inherit two copies of each gene (allele), eye color included.
- One copy comes from our mother, and one from our father.
- Both alleles are stored in our chromosomes (our genetic code) and can be passed on to our children, but only one presents in how we look.
Dominant genes present while recessive genes “hide out” in the DNA code for a chance to pass on to future generations. Generally, darker colors are the dominant traits, while lighter colors are recessive, so a person with one brown-eyed gene and one blue-eyed gene will have brown eyes.
Blue eyes + blue eyes = 100% chance of blue eyes Brown eyes + blue eyes = 50% chance of blue eyes, but only if the brown-eyed parent carries a blue-eyed gene. If not, the chance is 0% Brown eyes + brown eyes = 25%, but only if both parents carry the blue-eyed gene. If not, the chance is 0%
It is important to remember that this theory is a simplified version of what really happens at the genetic level. Human eye coloring is actually controlled by a complex genetic process and there are many different eye colors other than just blue eyes and brown eyes.
How common is it for mixed children to have blue eyes?
Predicting Your Baby’s Eyes – A more realistic look at eye colors offers the following possible combinations: Brown eyes + brown eyes = brown eyes, hazel eyes, green eyes, or blue eyes Brown eyes + hazel eyes = brown eyes, hazel eyes, green eyes, or blue eyes Brown eyes + green eyes = brown eyes, hazel eyes, green eyes, or blue eyes Brown eyes + blue eyes = brown eyes, hazel eyes, green eyes, or blue eyes Hazel eyes + hazel eyes = hazel eyes, green eyes, or blue eyes Hazel eyes + green eyes = hazel eyes, green eyes, or blue eyes Hazel eyes + blue eyes = hazel eyes, green eyes, or blue eyes Green eyes + green eyes = green eyes or blue eyes Green eyes + blue eyes= green eyes or blue eyes Blue eyes + blue eyes = blue eyes So really, any combination can result in a blue-eyed child, but only if there is blue eyes somewhere in one of the parents’ ancestral lines. Looking to learn more about your genetics and how they impact everything from your microbiome to your appearance and hormones? Our partners at Nebula Genomics can help you understand your genome, explore your ancestry, and learn about your inherited traits. Check out their offerings here.