What gives a person their eye color?

Question

My friend Corey wants to know the answer to this question. His ancestors all have different eye colors then him so it's bugging him lol.

Answer 1

In humans three genes involved in eye color are known. They explain typical patterns of inheritance of brown, green, and blue eye colors. However, they don't explain everything. Grey eye color, Hazel eye color, and multiple shades of blue, brown, green, and grey are not explained. The molecular basis of these genes is not known. What proteins they produce and how these proteins produce eye color is not known. Eye color at birth is often blue, and later turns to a darker color. Why eye color can change over time is not known. An additional gene for green is also postulated, and there are reports of blue eyed parents producing brown eyed children (which the three known genes can't easily explain [mutations, modifier genes that supress brown, and additional brown genes are all potential explanations]).

The known Human Eye color genes are: EYCL1 (also called gey), the Green/blue eye color gene, located on chromosome 19 (though there is also evidence that another gene with similar activity exists but is not on chromosome 19). EYCL2 (also called bey1), the central brown eye color gene, possibly located on chromosome 15. EYCL3 (also called bey2), the Brown/blue eye color gene located on chromosome 15. A second gene for green has also been postulated. Other eye colors including grey and hazel are not yet explained. We do not yet know what these genes make, or how they produce eye colors. The two gene model (EYCL1 and EYCL3) used above explains only a portion of human eye color inheritance. Both additional eye color genes and modifier genes are almost certainly involved.

Answer 2

It has to do with 2 things:
What eye color certain relatives have.
The dominance/recessiveness of that eye color.

Google "Punnet Squares" and go to some of the samples.

I actually calculated the probability of my daughter having hazel eyes using the Punnet Squares and came up with 25%. I have hazel, but hazel is recessive. My ex (her biological father) has brown & everyone in his family has brown. Also, brown is dominant. Apparently, there is a hazel eye gene in there somewhere!

Anyway, try looking at the Punnet Squares examples. Good luck!

Edited to add:
Punnet squares is what Weechi was talking about above. Don't you hate it when you just can't remember something? I do that all the time.

Answer 3

genetics. did you ever do those box diagrams in school...with the big T and the little t? i forget what it's called, but they determine the likelyhood of you inhereting certain traits from your parents. like....if all your grandparens have brown eyes, and your parents have brown eyes....if you end up with blue eyes, be suspicious! i think it doesn't work the other way though. like....blue is the most rare, but if everyone in your family has blue eyes, genetically, i think it's still possible for you to have brown eyes.

this is just what i remember from high school science..like, a long time ago. i'm sure someone else can give you a more acurate answer. but it is genetics.

Answer 4

Genes determine eye color. Blue is recessive and brown is dominant, and that's why more people have brown eyes than blue.

Answer 5

hahah it has to do something with Genetics ... and the dominate/ressesive jeans of ur parents/grandparents etc...

Personally, my eyes change colors depending on how much light is coming in/out of the room that im in...

usually there dark green but with a lot of light, they turn grey/blue

<3 olivia

Answer 6

On one of the chromosomes, there is a spot, where the general eye colour is determined.

As you have two chromosomes and therefore two genes, it depends on the alleles you inherit from your parents. An allele are different types of the same gene.

For instance, Brown eyes and blue eyes. The brown eye gene is usually labelled B, the blue eye gene b.

Some alleles are dominant over other alleles. Some are partially expressed, some are not.

Brown eye gene is dominant over Blue eye gene.

Two alleles of the same type are called homozygous, two of different types are called Heterozygous.

To have blue eyes, you must have two blue eye alleles.

To have brown eyes, you can have one brown eye and one blue eye allele or have two brown eye alleles.

So simple charts can explain how inheritance works.

A mother with two alleles for Brown and a father with blue eyes

Mother-----B------B
Father
---b---------Bb----Bb
---b---------Bb----Bb

Mother who has Heterozygous brown eyes and Father who has blue eyes

Mother-----B------b
Father
---b---------Bb----bb
---b---------Bb----bb

In the first chart, all the children will have brown eyes.
In the second chart, the children have a 50% chance of having blue eyes and 50% of having brown.

This is complicated because we are all Chimera. Everyone has patches of cells in them, that came from their mother, their mother's mother and possibly several generations of mother's mother's cells.

Blood for instance has three common alleles on the genes. O, A and AB. O is recessive to A and B. A and B both express themselves. So someone with AO shows up as A, someone with BO shows up as B and only those with OO show up as O. Someone with AB shows both AB.

There have been a number of cases where an ovary or testes, has a set of these cells making them up. Also sometimes these are found in the blood marrow, giving false information on the genetic complement of the person.

There was one case recently, where the mother had type O blood, or OO, the Father had type O blood, or OO, but one child was Type A and the other was Type B. On investigating the woman's ovaries, it turned out that one of them was composed of the cells from her mother, who was Type A blood, or AO. The Man, had one testes that when they took samples from it, had his mothers chromosomes in it, they were not XY as expected but XX. and his mothers blood type that was type B.

So while blood typing is often correct, it isn't always.

And eye colour is even more complicated, because there are modifying genes to the eye colour expressed.

For instance, Grey eyes, green eyes, black eyes, violet eyes, are not caused by different alleles as far as I remember, but are caused by modifying genes. For instance, skin, has 9 different genes, that have multiple alleles that can exist there. Each of these can modify the colour of the eyes as well.

An example of this modifying gene is hazel or green eyes. To express you need one B for Brown, and one b for blue, and the modifying alleles. If you only have one of these modifying alleles your eyes are hazel, if you have two, they are green.

They have recently mapped many of these modifying genes, but I haven't had access to the results yet to determine how to explain the results.

Answer 7

Apparently it is dna, whatever dna your mother and father give to you that is what determines your eye colour.

Answer 8

pssssttt...purely between you and me *whispers* Touz has colourless eyes....human beings says it fairly is why she grew to alter into queen of this area.. the others have been to scared to look her into the eyes!! :)

Answer 9

DNA... EX: I have a red headed baby and no red hair on father's or mother's side....

Answer 10

Does he look like anybody?