Phenotypes and Genotypes for human eye colours.

[Beorn]

Phenotypes and Genotypes for human eye colors

Part of the study of genetics involves being able to predict the appearance (phenotype) and genetics (genotype) of the offspring of animals or people.

Sometimes this is just for fun, such as breeding dogs to get a certain color, but sometimes it is very serious, as when dealing with diseases that can be passed from parents to their children. Here is an example of what we know about the genetics of eye color.

There are three known human eye color genes named: EYCL1 (gey), the Green/blue eye color gene, located on chromosome 19. EYCL2 (bey1), the central brown eye color gene, possibly located on chromosome 15. EYCL3 (bey2), the Brown/blue eye color gene located on chromosome 15.

A role has also been suggested for the Melanocortin Receptor Gene (MCIR) on chromosome 16. A second gene for green has also been postulated. Other eye colors including black, grey, and hazel are not yet explained. We do not yet know what these genes make (except MCIR), or how they produce eye colors.

The two gene model (EYCL1 and EYCL3) used here clearly does not explain more than a portion of human eye color inheritance.

Two gene model: There are two genes involved in eye color. One gene has Dominant Brown or recessive blue states, the other has Dominant Green or recessive blue states. We further assume that Brown in the first gene will swamp out Green or blue from the second gene, and Green from the second gene will swamp out blue from the first gene. Because chromosomes come in duplicate pairs, each parent has two copies of each gene.


<table bgcolor="#a6caf0" border="0"> <tbody><tr> <td bgcolor="#a6caf0"> Possible Phenotypes and Genotypes under the two gene model </td> </tr> </tbody></table> <table> <tbody><tr> <td><center>http://www.athro.com/evo/gen/blueeye.jpg</center></td> </tr> <tr> <td><center>Phenotype: Blue Eyes</center></td> </tr> <tr> <td><center>1 Possible Genotype:</center></td> </tr> <tr> <td> <table> <tbody><tr> <td><center>Gene: bey2</center></td> <td><center>Gene: gey</center></td> </tr> <tr> <td>Chromosome 15 Copy 1: blue
Chromosome 15 Copy 2: blue</td> <td>Chromosome 19 Copy 1: blue
Chromosome 19 Copy 2: blue</td> </tr> </tbody></table> </td> </tr> </tbody></table> <table> <tbody><tr> <td><center>http://www.athro.com/evo/gen/greeneye.jpg</center></td> </tr> <tr> <td><center>Phenotype: Green Eyes</center></td> </tr> <tr> <td><center>2 Possible Genotypes:</center></td> </tr> <tr> <td> <table> <tbody><tr> <td><center>Gene: bey2</center></td> <td><center>Gene: gey</center></td> </tr> <tr> <td>Chromosome 15 Copy 1: blue
Chromosome 15 Copy 2: blue</td> <td>Chromosome 19 Copy 1: Green
Chromosome 19 Copy 2: Green</td> </tr> <tr> <td>Chromosome 15 Copy 1: blue
Chromosome 15 Copy 2: blue</td> <td>Chromosome 19 Copy 1: Green
Chromosome 19 Copy 2: blue</td> </tr> </tbody></table> </td> </tr> </tbody></table> <table> <tbody><tr> <td><center>http://www.athro.com/evo/gen/browneye.jpg</center></td> </tr> <tr> <td><center>Phenotype: Brown Eyes</center></td> </tr> <tr> <td><center>6 Possible Genotypes:</center></td> </tr> <tr> <td> <table> <tbody><tr> <td><center>Gene: bey2</center></td> <td><center>Gene: gey</center></td> </tr> <tr> <td>Chromosome 15 Copy 1: Brown
Chromosome 15 Copy 2: Brown</td> <td>Chromosome 19 Copy 1: Green
Chromosome 19 Copy 2: Green</td> </tr> <tr> <td>Chromosome 15 Copy 1: Brown
Chromosome 15 Copy 2: Brown</td> <td>Chromosome 19 Copy 1: Green
Chromosome 19 Copy 2: blue</td> </tr> <tr> <td>Chromosome 15 Copy 1: Brown
Chromosome 15 Copy 2: Brown</td> <td>Chromosome 19 Copy 1: blue
Chromosome 19 Copy 2: blue</td> </tr><tr> <td>Chromosome 15 Copy 1: Brown
Chromosome 15 Copy 2: blue</td> <td>Chromosome 19 Copy 1: Green
Chromosome 19 Copy 2: Green</td> </tr> <tr> <td>Chromosome 15 Copy 1: Brown
Chromosome 15 Copy 2: blue</td> <td>Chromosome 19 Copy 1: Green
Chromosome 19 Copy 2: blue</td> </tr> <tr> <td>Chromosome 15 Copy 1: Brown
Chromosome 15 Copy 2: blue</td> <td>Chromosome 19 Copy 1: blue
Chromosome 19 Copy 2: blue</td> </tr> </tbody></table> </td> </tr> </tbody></table>
<table bgcolor="#a6caf0" border="0"> <tbody><tr> <td bgcolor="#a6caf0"> Example Crosses: </td> </tr> </tbody></table> Shown on a Punnett Square (http://www.athro.com/evo/gen/punnett.html)

Example 1
Parent 1: Brown Eyes, Genotype: bey2: Brown-blue, gey:blue-blue
Parent 2: Blue Eyes, Genotype: bey2: blue-blue, gey:blue-blue

<table> <tbody><tr> <td>bey2:
gey:</td> <td>Brown
blue</td> <td>Brown
blue</td> <td>blue
blue</td> <td>blue
blue</td> </tr> <tr> <td>blue
blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> </tr> <tr> <td>blue
blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> </tr> <tr> <td>blue
blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> </tr> <tr> <td>blue
blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> </tr> </tbody></table>

Each child has 50% probablility of brown eyes and 50% probability of blue eyes. On average, about half the children of this cross will have brown eyes and the other will have blue eyes.

Example 2

Parent 1: Brown Eyes, Genotype: bey2: Brown-blue, gey:blue-blue
Parent 2: Green Eyes, Genotype: bey2: blue-blue, gey:Green-blue

<table> <tbody><tr> <td>bey2:
gey:</td> <td>Brown
blue</td> <td>Brown
blue</td> <td>blue
blue</td> <td>blue
blue</td> </tr> <tr> <td>blue
Green</td> <td bgcolor="#cc9933">Brown-blue
Green-blue</td> <td bgcolor="#cc9933">Brown-blue
Green-blue</td> <td bgcolor="#99ff33">blue-blue
Green-blue</td> <td bgcolor="#99ff33">blue-blue
Green-blue</td> </tr> <tr> <td>blue
Green</td> <td bgcolor="#cc9933">Brown-blue
Green-blue</td> <td bgcolor="#cc9933">Brown-blue
Green-blue</td> <td bgcolor="#99ff33">blue-blue
Green-blue</td> <td bgcolor="#99ff33">blue-blue
Green-blue</td> </tr> <tr> <td>blue
blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> </tr> <tr> <td>blue
blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> </tr> </tbody></table> Each child has 50% probablility of brown eyes and 25% probability of green eyes and 25% probablity of blue eyes. On average, about half the children of this cross will have brown eyes, one quarter green eyes, and one quarter blue eyes.

Example 3

Parent 1: Brown Eyes, Genotype: bey2: Brown-blue, gey:Green-blue
Parent 2: blue Eyes, Genotype: bey2: blue-blue, gey:blue-blue
<table> <tbody><tr> <td>bey2:
gey:</td> <td>Brown
blue</td> <td>Brown
Green</td> <td>blue
Green</td> <td>blue
blue</td> </tr> <tr> <td>blue
blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#cc9933">Brown-blue
Green-blue</td> <td bgcolor="#99ff33">blue-blue
Green-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> </tr> <tr> <td>blue
blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#cc9933">Brown-blue
Green-blue</td> <td bgcolor="#99ff33">blue-blue
Green-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> </tr> <tr> <td>blue
blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#cc9933">Brown-blue
Green-blue</td> <td bgcolor="#99ff33">blue-blue
Green-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> </tr> <tr> <td>blue
blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#cc9933">Brown-blue
Green-blue</td> <td bgcolor="#99ff33">blue-blue
Green-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> </tr> </tbody></table>

Each child has 50% probablility of brown eyes and 25% probability of green eyes and 25% probablity of blue eyes. On average, about half the children of this cross will have brown eyes, one quarter green eyes, and one quarter blue eyes. About half of the children with brown eyes will carry the Green allele for the gey gene, and the other half will carry the blue allele.


Example 4

Parent 1: Brown Eyes, Genotype: bey2: Brown-blue, gey:Green-blue
Parent 2: Brown Eyes, Genotype: bey2: Brown-blue, gey:Green-blue

<table> <tbody><tr> <td>bey2:
gey:</td> <td>Brown
blue</td> <td>Brown
Green</td> <td>blue
Green</td> <td>blue
blue</td> </tr> <tr> <td>Brown
blue</td> <td bgcolor="#cc9933">Brown-Brown
blue-blue</td> <td bgcolor="#cc9933">Brown-Brown
Green-blue</td> <td bgcolor="#cc9933">blue-Brown
Green-blue</td> <td bgcolor="#cc9933">blue-Brown
blue-blue</td> </tr> <tr> <td>Brown
Green</td> <td bgcolor="#cc9933">Brown-Brown
blue-Green</td> <td bgcolor="#cc9933">Brown-Brown
Green-Green</td> <td bgcolor="#cc9933">blue-Brown
Green-Green</td> <td bgcolor="#cc9933">blue-Brown
blue-Green</td> </tr> <tr> <td>blue
Green</td> <td bgcolor="#cc9933">Brown-blue
blue-Green</td> <td bgcolor="#cc9933">Brown-blue
Green-Green</td> <td bgcolor="#99ff33">blue-blue
Green-Green</td> <td bgcolor="#99ff33">blue-blue
blue-Green</td> </tr><tr> <td>blue
blue</td> <td bgcolor="#cc9933">Brown-blue
blue-blue</td> <td bgcolor="#cc9933">Brown-blue
Green-blue</td> <td bgcolor="#99ff33">blue-blue
Green-blue</td> <td bgcolor="#66ccff">blue-blue
blue-blue</td> </tr> </tbody></table>

Each child has a 75% probablility of brown eyes and a 18.75% probability of green eyes and a 6.25% probablity of blue eyes. On average, about three quarters of the children of this cross will have brown eyes, three sixteenths green eyes, and one sixteenth blue eyes.
Source (http://www.athro.com/evo/gen/eyecols.html)

Click here for eye colour calculator. (http://www.athro.com/evo/inherit.html)

[Thrabul]

That's an interesting calculator. :)

http://museum.thetech.org/ugenetics/eyeCalc/eyecalculator.html

[Tabiti]

Blue - 11.2%
Green - 38.7%
Brown - 50%

[Aemma]

These calculators are pretty nifty. It's just too bad that they can't explain a grey eye colour yet though. Oh well, I guess I'll just have to continue to feel special. :P :D

What I've noticed about the colour brown though is that there are so many shades of this colour, it makes for a pleasant experience to just gaze into another's eyes and examine the base colours. I know that my son's eyes look like milk chocolate and in a certain light and with his hair colour (dark copperish auburn) and certain colours of clothing that he wears, his eyes will almost appear an orangey-brown, russet almost. Truly spectacular! :)

Eyes, more than just a mirror to the soul but an interesting way of discovering the beauty and richness of colour. :)

[Susi]

100% blue all the way :D

[Angantyr]

Blue-eyed parents, blue-eyed siblings,blue-eyed future wife. Calculation for children's eye colour...100% blue-eyed.

I probably could have done that without the calculator. ;)

[Susi]

Blue-eyed parents, blue-eyed siblings,blue-eyed future wife. Calculation for children's eye colour...100% blue-eyed.

I probably could have done that without the calculator. ;)

Then again there could always be up the line some sort of unsavoury colour like... GREEN :O

[Gooding]

100% chance for my children to have blue eyes!

[vp01]

anybody got haircolor calculator??

[Arne]

So please someone explain one part is blue and the other one is brown and the Child is brown-green.

[Majar]

Too bad it doesn't take into consideration all the mixed colors like hazel, grey-green, blue-green, etc and the dark/light variations.

[poiuytrewq0987]

My eyes are hazel while my parents' eyes are brown. My maternal grandmother has blue eyes, and my paternal grandmother too has blue eyes (both dead now btw). My eyes are not brown at all it changes all the time sometimes it's pred brown, sometimes it's pred green. So my eyes are not represented at all on the chart. :p Although if I were to have brown eyes then the chance of passing on brown eyes would be 76% with green and blue at 13%.