Do you or does someone you know have different-colored eyes? When you meet someone with one blue and one brown eye, for example, it sometimes takes a minute to register why they may seem a little “not quite right.” But then, when you look a little closer, you see how beautiful and unique this trait is. It’s a rare phenomenon called heterochromia. So is it always DNA-caused or can it happen for other reasons? Let’s have a look.
Where Eye Color Comes From
First, a little bit about eye color. A pigment called melanin determines hue, and eye color develops in the eight or so weeks following birth.
- People with a lot of melanin in their irises have brown eyes.
- People with very little melanin in their irises have blue or grey eyes.
- People with middling amounts of melanin sport hazel or green eyes.
Newborns’ eyes all look blue because it takes weeks for the genetically-designated amount of melanin to ‘color in’ their irises. Today’s scientists believe that two genes control eye color (not just one), and it is how these genes interact that provides the full range of colors in people’s peepers. Which brings us to folks who have two different-colored eyes.
FUN FACT: Did you know that blue eyes were originally caused by a genetic mutation some 6,000 to 10,000 years ago? Scientists believe that everyone originally had brown eyes. That original mutation ended up greatly affecting the world’s DNA pool, didn’t it? READ MORE ABOUT IT HERE.
Different Types of Heterochromia
‘Heterochromia’ is a Latin term meaning ‘different colors,’ which perfectly describes this trait. There are actually three distinct categories of heterochromia, although some people may have a combination of two or three:
- Complete (each eye is a different color).
- Sectoral (a segment of one or both irises is a different color).
- Central (a different color surrounds the pupil).
How Does Heterochromia Happen and Why?
There are lots of different reasons! In the vast majority of cases, people are born with different-colored eyes, but there are times when heterochromia is caused by something else. Do you or someone you know have different-colored eyes? If so, this unique characteristic most likely happened from one of the reasons listed below.
Family DNA: Usually, if the trait is apparent from babyhood, then it came from the family gene pool. In fact, since it’s a dominant autosomal trait, chances are good one of the person’s parents has it too.
Trauma during Birth: If facial trauma occurs around the time birth, it may prevent melanin from ‘coloring’ the eye in the affected area of the face.
Genetic Mutation: Sometimes, a mutation in one of the genes regulating eye color may occur during embryonic development.
Disease: There are certain diseases such as Horner Syndrome that may cause heterochromia during a person’s lifetime.
Injury: Heterochromia that happens later in life is usually caused by eye injuries or specific types of medication.
Chimera: Under extremely rare circumstances, a person could be a chimera (when they contain separate DNA from an undeveloped twin) and have eyes with different colors as a result.
The Bottom Line
Keep in mind that traits like heterochromia or other physical characteristics are never absolute proof of paternity-a DNA paternity test is a much more scientific and reliable resource for determining a biological relationship. Too often, a mother might say, “But my child looks just like this man I slept with and not like the other one,” only to find out through DNA testing that the child is the biological offspring of the man he/she looks nothing like! So be very careful about making assumptions about a biological relationship based only on heterochromia.
Our bodies are wonderful things, and little blips in our DNA can sometimes have physical consequences-like double eyelashes! Over time, genetic mutations are no longer mutations at all, but are considered ‘normal’-like blue eyes. If you or someone you know is lucky enough to have different-colored eyes, embrace its unique look!
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Alle. “7 Beautiful Mutations: Which Ones Do You Have?” XoVain. Time, Inc., 3 Oct. 2013. Web. 07 July 2016. <http://www.xovain.com/how-to/7-beautiful-mutations-which-ones-do-you-have>.
Bryner, Jeanna. “One Common Ancestor Behind Blue Eyes.” LiveScience. TechMedia Network, 31 Jan. 2008. Web. 07 July 2016. <http://www.livescience.com/9578-common-ancestor-blue-eyes.html>.
Gross, Susan J. “How Does Someone Get Two Different-colored Eyes?”Scientific American. Nature America, Inc., 3 Nov. 2001. Web. 07 July 2016. <http://www.scientificamerican.com/article/how-does-someone-get-two/>.
Heiting, Gary, OD. “Why Do Some People Have Two Different Colored Eyes?”All About Vision. Access Media Group, LLC., Apr. 2016. Web. 07 July 2016. <http://www.allaboutvision.com/conditions/heterochromia.htm>.
Melina, Remy. “Why Do Some People Have Differently Colored Eyes?”LiveScience. TechMedia Network, 25 Jan. 2011. Web. 07 July 2016. <http://www.livescience.com/32954-why-do-some-people-have-differently-colored-eyes.html>.
Tammy Kendall says
How do I find out if I have 2 sets of DNA? I was born with 1 brown and 1 green. As far as my parents know, no one in the family had 2 different colored eyes.
Hi, Tammy. Testing specifically for chimerism (2 sets of DNA in one person) is very expensive, so it’s usually discovered by chance while doing other testing. Chances are good, if you have heterochromia, that it’s just a genetic coincidence. Lucky you because it’s beautiful!
I was born with a brown eye and a blue eye, I was told I was suppose to be a twin. How will I ever know?
The blue eye eventually turned hazel and my brown eye is almost the color of my pupil.
i have the exact same thing
Hello Jenna, my name is Meg and I am a chimera twin. My mother would have had triplets, but around the forth to fifth day for lack of a better word I absorbed a embryo that would have been a sister. I have a twin brother and we’re 32yrs. Chimera twin people have sometimes duplicate organs, also organs with different DNA profiles. The best ways to confirm your a chimera are both radical and expensive. They can get a diagnosis through a CAT SCAN ( checking for extra organs), spinal tap ( checking for multiple DNA types), tissue samples, blood tests. Since the above options are unrealistic I would instead do the following; Chimera people like myself often have mosaic skin patterns. I also have a talon cusp on an maxillary anterior tooth. Look for those things, if you do have one or both these then I’d suggest seeing a specialist doctor to confirm. This is a very rare condition.
My name is Susan
I have one blue eye and one green eye.
I inherited it from my mum and dad.
My mum had blue eyes.
My father had green eyes.
My brother and sisters do not share the same problem, with there eyes, has me.
I had it from child birth.
When I was a child I felt it is only me with 2 different coloured eyes, I think nobody else has this problem about them, except me.
It’s not a problem. It’s a beautiful thing. You are lucky to be so unique….Perhaps not in your family, and although rare….many people have some type of Heterochromia….I have central heterochromia….around both of my pupils…is a different colour than the rest of my iris. Take care…………..cheers.
Thanks Susie, for your message, people used to tease me about my heterochromia, I was a very sick child when I was young, I was a lonely child, everybody said I was not perfect. My grandmother said when I was aged 5, I could use eye changing eye drops.
I have a blue eye and a green eye……I used to hate it but it has grown on my now.
I have one eye that not the same as the other, both change color daily and have been many colors,blue ,green,brown,and many mixes of each .I was born with this,my grandmother also had this,and I’ve been told that my daughter’s children will have it too.
MY BRO IN LAW IS AA VERY DARK SKINNED AND HAS ONE BROWN EYE AND ONE SKY BLUE EYE, HIS BROTHER AS DARK SKINNED HAS BOTH EYES SKY BLUE, IT’S HAUNTING
I have blue eyes the top quarter of one is brown and the bottom half of the other is brown. My son has blue grey eyes with the top of one brown. Dad is blue eyes and mom is hazel.
Hi, Kerri. Sounds beautiful! :-)
Wooow that sounds really cute.. It’s AMAZING the way dna/genetics works. I’d love to see your eyes sounds so cool. Sounds like both of your parents has very strong genes that had to come to an agreement and give you both of their eye color.. I would love to have two different color eyes, I love them. I just never seen a half and half, blessed.
so my right eye is brown with a green inner rim near the pupil. My left eye is green with a brown inner rim near the pupil. its hard to explain, it would be easier if i could import pictures. Anyway does that mean i have heterochromia iridum? cause they are pretty much two different colors.
It sure sounds like it, Maeson!
By the way, we cannot make personal email addresses public, both for our protection and yours.
my left eye is blue,,sometimes its gray,,my right eye is brown,,sometimes its half green and half brown,,my mother and oldest brother had brown eyes,,my dad and my 2nd to oldest brother has green eyes,,i guess i got all their color eyes,,except for the blue eye,,my aunt does have blue eyes,,my moms sister,,
You can say you got the best and a little bit of everyone. It’s cool how it works. Even if your aunt didn’t have blue eyes (although she do) it could’ve have reached way back to a relative you never knew about. It’s does give you an idea of which side of the family the blue comes from. (Mom/Dad)
Hi Dee. Your eye color sounds similar to mine. My left eye is blue/grey, and sometimes green, (changes) My right eye is green, with some brown, and also changes. My Mom had brown eyes, and my Dad green. I’m not sure in the gene pool where the blue eyes came from!
i was born with one brown eye and one hazel eye.
i was born with one brown eye and one hazel eye. my great grandpa had different colored eyes and i do have a twin. my eyes change color of my emotions.
Hello. My name is Michael. I have sectoral heterochromia (hope that’s spelled right) I have light blue eyes but there is a very noticeable golden spot in my right eye. I believe that mine was caused by trauma during birth. My shoulders were unusually broad. The doctor had to use an instrument to help me out of there. My first photo shows the faint bruises left by the “salad tongs”. I was told that when I was young that it was attractive? Now it’s just interesting. Ha ha. Oh, and no, I do not need help. Jus sayin’
Thanks for sharing, Michael! I’ll bet it gives you a really unique look. :-)
i was born with two different colored eyes. my left eye is brown and my right eye is hazel.
i was just wondering what i have or what it means, and also my eyes changes color when i’m sad it turns bright green and when i’m happy its turns green with a little bit of blue. Just askin
My name is Krisna, i am from Asia Cambodia. i born with two completedly difference eye colors, one brown and one blue. the special about it the blue one changing color slightly. when in the dark or shad the blue one become dark blue and when it in the light it become light blue. any idea? thanks
I was born with blue-gray eyes that turned solid brown within a few days. They stayed solid brown until my mid fifties when I began taking estradiol as MtF transgender hormone replacement therapy, then my eyes both suddenly changed colors within 30 days to central heterochromia with green/hazel on the outside 2/3 of the irises and a very small amount of brown still there immediately surrounding the pupils, perhaps 1/3 of the iris area. My doctor says he believes I am a tetragametic chimera since I also have a female shaped pelvis, and possibly both male and female gonadal reproductive system tissue
Patricia Keene says
can you have a brown part removed from one eye to match a green eye?
Hi, I’m Alyson I have blue eyes, but a quarter of my left eye has green in it. What is this?
Hi, Alyson. This is a form of heterochromia. The two most likely reasons are it’s either genetic, or there may have some kind of trauma to your eye when you were born. Either way, I’ll bet it’s beautiful!
Hi, I am Holly 47 and I have complete Heterochromia. One blue and one green. My mom has green and dad had blue. We always believed it was a fluke. Both of my sisters have blue. My mom tells a joke about having three kids and one green eye in her kids! Anyway, has anyone ever been told that this condition can cause eyesight loss?, do to the lack of pigment in my blue eye. Years ago a resident told me that I can continue to lose pigment because of my Heterochromia. I always worry about it, especially because I am extremely sensitive to light, even artificial light. People think I am crazy because I always wear shades and I hate sunlight. I will not go anywhere without them. My eyes are sensitive but seem fine. Thanks, Holly
So both of my parents have hazel eyes while one of my older brothers has hazel and the other has these piercing blue eyes. Me on the other hand have one full bright ice blue eye while the other is half gray blue and half hazel that sometimes changes to green & green-blue. When the light hits them, there’s gold specks. I always wonder if there’s others like me out there. But I’m still amazed by my eyes whenever I look in the mirror every morning.
yah im simpler but im, not the same mine changes color and shades of color but u should know mine have amber and red too with flecks of green and blue
Hi, one a question about heterochromia. Exactly, where and how does this mutation occur? In what part of genoma, in chromosome, etc. Gracias.
I have two different eye colors and my right eye is blue but changes to gray and gets this red too and it slowly begins to take up half of my eye then I get this pie chat look were there is a ring of grey around my eye and some green too my other eye looks the same but with grey ora darker blue I have a completely different shade of blue I have a completely different eye colour in each eye color my left eye is blue or grey it goes back and forth my right is green but changes hazle and light or dark green I’m not sure what form heterochromia I have so I’m so confused can some 1 clear it up
My grandson has one brown eye and one half brown/half hazel which sometimes goes green. It looks amazing.
I just accidentally stumbled on all of this… I have grey eyes, and both of them have a gold color around the pupils, which “radiates” into the irises like a “sun.” They have been that way since I was Born. I also have a problem with my skin, that none of the “doctors” I’ve spoken to can explain, and most won’t even try, except to accuse me of “poor hygiene.” This info has been confusing, and hard to locate, but it gives me some hope that I might finally know why..? How do I find out if these things are “connected..?”
I have one blue one brown eye. The only one in my family that had that. The only other one was my cat.lol
I was born with one green eye and the other blue with two lines of hazel how rare is this and is there a specific name for this.
Anne J says
My brother has green eyes with a slice of brown or hazel in one eye. I have hazel eyes – but one seems more of a green hazel and the other a brownish hazel – but I thought it was my imagination.
I have basically 3 colors in my eyes. I have blue on the outside, little bit of an aqua green in the middle, then light brown surrounding my pupil. What is this called and how is it caused???
HomeDNA Identigene says
Hi, Abigail. You have a form of heterochromia and this article can explain a lot of it for you. Sounds beautiful!
Is it possible for a set of twins to be born where one has one brown eye and the other to just have blue eyes. I am writing a story where the sister has the mismatching eyes and her brother has the normal blue eyes. I just want my facts to be straight or else, what’s the point?
HomeDNA Identigene says
Hi, Chris. Yes, it’s most definitely possible for fraternal twins to have different eye colors. They share 50% of their DNA, like regular siblings, and not 100%. Their eye color depends on the genes they happen to inherit from their parents, and those genes aren’t going to be the same for each twin.
Hi. I have complete hx. My left is blue and my right is brown. Since birth. Of course in the mirror its opposite so I always say bLue left, bRown right, it’s the only way I remember! Still at 46! When I was in my early teens, my brown eye turned green and both looked normal which was a relief at school for a bit, then they reverted to type and the childhood names started “chief odd ball” freek” “witch”, you know them. Now in my later life, my eyes are a little less bright but are still noticed, now from inquisitivness rather than mockery. Is it DNA? My younger sister born with brown eyes, one of which with a blue mottle. My other sis has green eyes. My mother has blue and my father brown eyes. No one else in my family has hx that I am aware of. None the wiser other than my physician saying that my mapped hx is 1 in 3m people. Any other stats out there for full different coloured eyes?