Where’d the green-eyed monster come from?
If both parents have blue eyes, the children will have blue eyes. True or False?
False. It’s rare, but blue-eyed parents having brown-eyed children does happen. Why? Well, it’s complicated, but we can start by telling you that what you learnt at school, assuming you are of a certain age, is wrong.
The human eye comes in many different shades and intricate, unique iris patterns. Eye colour comes from a combination of two black and yellow pigments, melanin, in the iris.If you have no melanin in the front part of your iris, you have blue eyes. An increasing proportion of the yellow melanin, in combination with the black melanin, results in shades of colours between brown and blue, including green, grey and hazel.
Brown is the most frequent eye colour worldwide.
Mix it up
It was originally thought that eye colour was a simple Mendelian trait, that it was determined by a single gene. But modern science has shown that eye colour is not at all that simple.
Eye colour is a polygenic trait; it is determined by multiple genes and the interactions between them. This is what makes it possible for two blue-eyed parents to have brown-eyed children. There is evidence that up to 16 genes can influence eye colour; the two most important genes are OCA2 and HERC2.
In the simplest models of eye colour, there are two genes involved. For each gene, we inherit two copies, one from our mother and one from our father. (This model is too simple to explain a lot of things, but it will suit our purposes.)
Why are our kids’ eyes different colours?
Let’s look at why a blue-eyed parent (dad) and a brown-eyed parent (mum) and can have brown, green, and blue-eyed children.
For gene 1, OCA2, there are two possibilities: brown or blue. The brown version of gene 1 is dominant over the blue one. Dominant means that if at least 1 of your two copies is brown (Bb), then you will have brown eyes. Geneticists represent the different versions of the eye colour gene as B for brown and b for blue (the capital letter is the dominant, the lowercase, recessive). So brown eyes are either Bb or BB and blue eyes are bb.
For gene 2, there are two possibilities, green or blue. Green is dominant over blue. Green eyes can be GG, or Gb, while blue eyes are bb. Brown is dominant over green, so if you have a B version of gene 1 and a G version of gene 2, you will have brown eyes.
The possible gene combinations that can give you brown, green, or blue eyes are shown in the chart.
Back to the green or blue-eyed children. Dad can only be bb bb as he has blue eyes. Since mum has brown eyes, she could have any of six different possibilities. But since they have brown-eyed, green-eyed and blue-eyed children, the most likely possibility is that mum is Bb Gb, meaning she has brown eyes but carries genes for both blue and green eyes.
What colour will your baby’s eyes be?
How eye colour is inherited is far more complicated than what was thought back in the day.
Generally though, it’s far more likely for two brown-eyed parents to have a blue-eyed child than for two blue-eyed parents to have a brown-eyed child. This is because the generally less dominant blue-eyed trait can be passed along by brown-eyed people until the genes for the lighter eye colour happen to match up, possibly many generations later.
So, to try and clarify things, let’s think about this situation. Someone with brown eyes may be carrying one blue allele and one brown allele, so a brown-eyed mother and a blue-eyed father could give birth to a blue-eyed child. Now mix in a third green allele, which is dominant to blue, but recessive to brown. If the brown-eyed mother carried the green allele (bG), she could pass the green allele on 50% of the time, so when married up with the father’s blue allele, they could have a green-eyed child.
Eye colour is much more complicated than our explanation here, and involves genes that determine the amount of pigment in your eyes, as well as genes that can modify even dominant alleles, but I hope it clears things up for you.
For more information, this site is very helpful.
If you have or any other questions about eye colour or eyes in general, askourNewmarket optometristsor ouroptometrist in Henderson.They are pretty clued up on all things related to eyes and optometry.
FAQs
In fact, there are so many potential eye colors and so many factors that determine eye color, that it's practically impossible to predict the eye color children of any couple will have, even if both parents have, say, blue eyes or brown eyes.
Can you predict your child's eye color? ›
Eye color is a genetic property, but it's not quite as cut-and-dried as you might have learned in biology class. Two blue-eyed parents are very likely to have a blue-eyed child, but it won't happen every single time. Two brown-eyed parents are likely (but not guaranteed) to have a child with brown eyes.
How do I know if I have blue or hazel eyes? ›
Hazel eyes are generally a combination of brown, green, and gold. Sometimes, blue or even amber can make an appearance in hazel eyes, too. Often, hazel-colored eyes have a different hue around the pupil than on the eye's outer rim. This gradient of color can give hazel eyes a “sunburst” effect.
What are the eye color possibilities if they chose to have children? ›
For example, the brown allele is dominant, so if both parents have dark eyes, their baby will likely have dark eyes. If both parents have blue eyes, the odds are that their baby will also have blue eyes. If one parent has brown eyes and the other has blue, this leaves a 50/50 chance their baby will sport either color.
What is the colored part of the eye that can be brown green blue or grey? ›
What gives my eyes their color? Your eye color refers to the color of each eye's iris, a double-layered ring of muscle tissue around your pupil that controls how much light enters your eyes. The color of your iris depends on a few different factors between it and other parts of your eye.
Is hazel considered brown or green? ›
While all hazel eyes will have a combination of green and brown colors, the difference in dominant colors is why hazel eyes can appear either mostly green or mostly brown. This variety in color can cause some confusion, but as long as there is a mixture of green and brown in the iris, the eyes are hazel.
What determines the color of a child's eyes? ›
Eye color is determined by variations in a person's genes. Most of the genes associated with eye color are involved in the production, transport, or storage of a pigment called melanin.
Are my eyes grey or blue? ›
Gray eyes may be called “blue” at first glance, but they tend to have flecks of gold and brown. And they may appear to “change color” from gray to blue to green depending on clothing, lighting, and mood (which may change the size of the pupil, compressing the colors of the iris).
What is the rarest eye color? ›
Of those four, green is the rarest. It shows up in about 9% of Americans but only 2% of the world's population. Hazel/amber is the next rarest color after green. Blue is the second most common and brown tops the list, found in 45% of the U.S. population and possibly almost 80% worldwide.
Are hazel eyes rare? ›
According to the World Atlas, only about five percent of the world's population have hazel eyes—just behind the rarest eye color, which is green. The rarity of hazel eyes can be attributed to the intricate genetic factors involved in their development, which includes the combination of melanin and Rayleigh scattering.
If one biological parent has blue eyes and the other brown, then your child has a 50-50 chance of having permanently blue eyes. If both biological parents have blue eyes, then it's very likely that your child's eyes will be permanently blue.
What color will grey baby eyes turn? ›
Your baby's eye color may change over the first few months to a year. Newborns sometimes have dark blue or slate-gray eyes that gradually turn blue, green, hazel, or brown. A few children's eyes will continue to change color until adulthood.
Can blue eyes turn green? ›
The amount of melanin that's added to baby's eyes as she gets older influences eye color as well. “As they're growing, some children pick up more and more pigment in the back of the iris. The irises are going to become darker, so they'll change from bright blue to a dark blue to green or even to hazel,” Jaafar says.
Is eye color determined by mother or father? ›
Neither and both. It used to be believed that it would be by whoever has the dominant genes, however Scientists have found that eye Color is affected by multiple genes, and from both parents. Based on the parents genes they can calculate a probability, but probability is always a guess at best.
Is hair color determined by mom or dad? ›
While dark-haired parents tend to have dark-haired kids, hair color genetics is quite complex. Your hair color depends in part on how many genetic variants you inherit from both of your parents. If you have brown hair, your shade of brown depends on how many light and dark markers you inherit from your mom and dad.
What do hazel eyes look like? ›
Hazel eyes are usually a combination of brown, green, and gold, although they can appear to look like any of those colors at a distance. Hazel often means that the inside of an individual's iris is a different color than the outer rim, giving their eyes a bright, vibrant, multicolored appearance.
What is the prettiest eye color? ›
One thing these survey results have in common is that light-colored eyes — green, gray, blue, and hazel — are named as the most attractive eye colors in the world. In one large survey of more than 66,000 people, green was chosen as the most attractive eye color.
What is it called when your eyes are blue green and brown? ›
Heterochromia is when you have differently colored eyes or eyes that contain more than one color. ( Photo credit: Vchalup/Dreamstime) Most of the time, it doesn't cause any problems. It's often just a quirk caused by genes passed down from your parents or by something that happened when your eyes were forming.
Are blue green gray eyes rare? ›
Green eyes are rarer than gray eyes, but only by 1%. Around 3% of the world's population has gray eyes. Like blue eyes, gray eyes are caused by a lack of melanin in the iris.
Which parent determines a child'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 multiple genes interact also plays a role in determining eye color.
As more melanin develops, the eyes can darken to green, hazel, or brown. Predicting when your child's eyes will stop changing color can vary. “The range of time when a baby will develop their 'true' eye color varies, but it usually happens between six and nine months of age,” Dr. Zepeda says.
Can two brown-eyed parents have a blue-eyed child? ›
Flexi Says: Two brown-eyed parents (if both are heterozygous) can have a blue-eyed baby. If both the parents have brown eyes, then there is generally a 25% chance for their child to have blue eyes. Because both the brown-eyed parents have a recessive blue-eye gene and can pass it to the next generation.
Can you choose your unborn child's eye color? ›
While a baby's eye color can sometimes be predicted by looking at his or her parents' eyes or those of other relatives, genetic variations can lead to unexpected results. Currently, genetic engineering allows us to select our baby's gender and eye color as well as modify the risk of certain illnesses.
For gene 1, OCA2, there are two possibilities: brown or blue. The brown version of gene 1 is dominant over the blue one. Dominant means that if at least 1 of your two copies is brown (Bb), then you will have brown eyes. Geneticists represent the different versions of the eye colour gene as B for brown and b for blue (the capital letter is the dominant, the lowercase, recessive). So brown eyes are either Bb or BB and blue eyes are bb.
How eye colour is inherited is far more complicated than what was thought back in the day.