Can a Brown Eyed Person and a Blue Eyed Person Have a Baby With Blue Eyes?

Editor's Note (1/6/2021): Some information in this article is out of date. While it describes eye color as a simple trait adamant by 2 genes, scientists now know this is incorrect. Eye color is a complex trait that is influenced by many genes. While the truth is more complicated than described below, it is still truthful that brown heart color is more dominant to blue, and that the DNA for blue eyes can be hidden in a family unit for generations.

A lot of different colors can lurk behind someone's brown eyes. This is truthful fifty-fifty if an eye colour similar blueish hasn't been seen in a family for generations. The blue eyes could still exist hiding there, waiting for the correct fourth dimension to announced.

That right fourth dimension is when both parents happen to have that particular colour hiding out behind their brown. If merely ane parent has the correct stuff to pass on blue eyes, odds are none of the kids will end upwardly with blue eyes. But these kids could all withal have blue hiding backside their brown like that parent.

This is one mode that blueish optics can stay subconscious for hundreds of years before making a sudden, dramatic advent. Only one parent in each generation has bluish hidden behind his or her brown. At present, generation later on generation, anybody will have brownish eyes and some will have those hidden dejection.

Bluish eyes can stay subconscious in a family tree for hundreds of years

 The blue optics would go along getting passed down until finally one of these "carriers of blue eyes" had children with another parent that was a carrier too. Now their children would have a take a chance at blue eyes.

This is nearly certainly how the two of you ended up with a kid with blue eyes. You and your married man both have blue and at least one of you has green optics hiding behind your brown.

By chance, yous each passed a blue to i of your children and that child ended upwards with blue eyes. Well, that is almost how it worked…

Three Centre Colors, Two Genes

For something seemingly then elementary, eye colour is surprisingly circuitous. Even the simplest models of eye color that try to explain merely brownish, green, and blue need two genes.

The first gene determines whether or not you will have chocolate-brown eyes. If it says take brownish, and then the other factor doesn't matter. You will take brown optics.

If it says not to have brown eyes, and so the second factor kicks in. This gene will determine whether you will take green or blue eyes.

Ane way to remember virtually it is with cards. Imagine the first gene is a bill of fare that is always on meridian of the 2d one.

This offset cistron comes in two versions, brown and clear. If y'all have a brown card, you can't see the card underneath. It could be greenish, it could be blue…who knows?  The end result is brown optics.

If you accept the articulate card, so you lot can see what is underneath. And it will be either blue or green. Now y'all take bluish or green eyes depending on the underneath carte. Hither is what I hateful:

As you tin can come across, if y'all accept the chocolate-brown card (gene), you lot will have brown eyes no thing what is underneath. But if you have a clear card (not-chocolate-brown gene), and so the 2d card (gene) matters.

This is a very simplified version of how blue eyes can stay hidden in a family tree. Generation afterwards generation, at least one parent passes down a brown version of the get-go cistron. The blue stays hidden until 2 people with a hidden blueish happen to both pass a articulate and a blue to their child. Now the child has blue eyes.

But how tin can a brown eyed person pass a "articulate carte du jour?" Information technology is because we have ii copies of most of our genes. So instead of two cards, i for each factor, we need to call up about four cards, two for each cistron.

Ii Genes, Iv Copies

Getting back to our card instance, let'due south say that instead of one of each type of card, we accept two. So for the get-go gene you could accept 2 browns, a brownish and a clear or two clears. And for the second you could have two green, a light-green and a blue, or ii blues.

Again the chocolate-brown and articulate genes are always on meridian of the greenish and blue. But one difference is that now nosotros say that green is e'er on top of blue.

So if you have 2 browns, again yous take a brown menu on tiptop. And if you accept a articulate and a brown, and so you lot still can only run into brownish.

Y'all tin only get greenish or blue with two clear cards. When that happens, we can accept a expect at the cards underneath.

If there are one or ii greens, y'all have a green pile. But if both of the first gene are clear and the second blue, then you lot have blue.

OK, that was a lot of cards! Here are three examples:

In the kickoff, the brownish trumps everything. In the 2nd green wins out over blueish and in the last, blue wins out.

And so in genetics-speak, brown is dominant over green and blue, and dark-green is dominant over blue. Another way to say this is blueish is recessive to greenish and brown, and green is recessive to chocolate-brown.

Let'due south use these cards now to imagine your situation. Commencement off, y'all each have brown eyes so you have at least one brown. But yous also had kids with greenish and blue eyes so we know your second card has to exist the articulate ane. You lot each have one brownish and ane clear card.

Since you had a green and a blue eyed kid, we know you must each have a bluish and at least one of you has a green. Then one of you for sure has a green and a blueish and the other has either two blues or a green and a blueish.

At present we'll explain how your three kids concluded upwards with the center colors they did. Earlier doing that nosotros demand to remember one thing. Nosotros pass on only one of each of the ii pairs of cards to our kids.

So you will pass either a brown or a clear and either a blueish or a green. The same goes for your spouse. Each kid will become ii cards for you and 2 from your spouse then they will accept four (simply like you). Hither is what might have happened in terms of cards for the chocolate-brown eyed child:

As yous can meet, both the hubby and married woman in this example have one of each card. In this case. The husband passed a dark-brown and a dark-green card and the wife a clear and a blue. The child has chocolate-brown optics only could have blue or green eyed children considering of the clear card.

Here is one mode that each child could end upward with unlike colored optics:

For both the green and the bluish eyed kid, each parent had to pass a articulate card. Then the dark-green or bluish depends on whether a green got passed down or not.

Bringing It Back to Genes

Upwards until now I take been talking near cards but of course they are just a representation of genes. We have two eye color genes.

Gene 1 comes in two versions, brown and not brown. And gene 2 comes in two versions, green and bluish. Geneticists call different versions alleles.

Hither are our examples once more with genes added:

The kickoff gene, brown or not brown, is in the first pair of letters and the 2nd factor, dark-green or blue, is in the second pair. So Bb Gb has ane of each menu and since there is a brown, this person has brown optics.

Here is a listing of possible gene combinations (genotypes) and possible eye colors (phenotypes):

Genotype	Phenotype
BB bb	Brown
BB Gb	Brown
BB GG	Brown
Bb bb	Dark-brown
Bb Gb	Brown
bb GG	Dark-green
bb Gb	Green
bb bb	Bluish

So there you have it…probably way more than than y'all wanted! Recessive traits like blue eyes can prevarication dormant in the genes for hundreds of years waiting for the risk to awaken and be seen. That risk comes when two carriers come up together and have children.

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Source: https://www.thetech.org/ask-a-geneticist/brown-eyed-parents-blue-eyed-kids

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