where do blue eyes come from?

​‘... a curious condition which consists in a difference in the pigmentation of the two eyes...', '...regarded by the casual observer as a play or caprice of nature.'

Mutiple genes are responsible for variations in a person's eye color.

With semi-curly, shortish auburn-blonde hair, Thomas turned to look at me.

‘Look at his eyes!’ My friend proclaimed. ‘Look! His two eyes are different!' 

What is it? I asked.

‘They’re different colors!’

A strong jaw announced Thomas’ physical dominance in height and strength. Thomas, froze momentarily as I curiously turned upward to this giant - almost as tall as the doorway. Indeed, his eyes were different colors.

Slate blue, and as obvious as his now furrowed expression, jade-green-hazel in the other. 

Gene Heritage is an online DNA service allowing you to upload your raw data from AncestryDNA, FamilyTreeDNA, 23andMe to compile reports about your family's genes, traits such as blue eyes, and a gene's ancient origins. Gene Heritage helps you to create an insightful picture of your physical identity and your genetic inheritance. It is one player that aims to improve our understanding of ourselves. I previously covered Gene Heritage here and here.

Gene Heritage tests for nearly twenty genetic traits that influence who you are, including your eye color, perceptions of taste, sensitivity to smell and reactions to alcohol. Gene Heritage is offering you an insight into how you may have inherited certain traits not just from your parents but your grandparents too. You can build three-generation genetic family trees which show which genes have been passed down to a grandchild and the percentage of DNA a grandchild inherited from each grandparent.

Joseph Silver, creative director and co-founder of Gene Heritage says, ‘The Grandchild Report reveals what percentage of DNA a grandchild inherited from each grandparent.'  He adds, 'As you may know already, it’s not necessarily a 25/25/25/25 split. While a Grandchild Report can be generated with as little as 1 grandparent, 1 parent, and a grandchild, best results are achieved with more family members.’

If you have already uploaded your own DNA test result from AncestryDNA you can upload and purchase a report from Gene Heritage. Each report costs $8 per family member.  Below are examples of a Gene Heritage grandparent-child report:

Gene Heritage is able to show you how much of your DNA you inherited from your parents and grandparents. It’s easy to assume that you inherit a quarter of your genes from each grandparent, but realistically this is to a matter of degree. Source: Gene Heritage

With more DNA information on parents and grandparents uploaded to Gene Heritage, the better your DNA inheritance report will be. Source: Gene Heritage

To assist you Gene Heritage also has easy-to-understand explainers of each gene detected in your DNA, all of which are referenced:

In this example, Gene Heritage reports Jean inherited one "Light" allele of OCA2 from Rosalind, and inherited one "Dark" allele of OCA2 from Gregor. Source: Gene Heritage

Gene Heritage explains that, ‘blue, green, and grey eyes are lighter and contain less melanin. Hazel eyes are in the middle of the dark-light spectrum. Brown eyes have higher concentrations of melanin. Certain mutations in OCA2 lead to albinism, of which one trait is blue eyes.’ Source: Gene Heritage

Thomas, my high school colleague in my opening story likely had heterochromia. Heterochromia iridium (or binocular heterochromia) refers to a condition in which the iris in one eye has a different color the other. While the condition can be acquired (because of an injury to the eye), it can also be inherited due to variations in a major gene, OCA2. (This website briefly explains all the types and possible causes of heterochromia.)

There are famous living and historical figures with heterochromia. Actress Kate Bosworth and actor Henry Cavill have heterochromia. American ophthalmologist described heterochromia in 1918 as a, ‘...curious condition which consists in a difference in the pigmentation of the two eyes...', '...regarded by the casual observer as a play or caprice of nature.' Even Anastasius I, a Byzantine Emperor from years 491 to 518 had separately colored eyes and was also thought to have heterochromia.​​

In 2008, a team of scientists at the University of Copenhagen suggested that a genetic mutation in the OCA2 gene that took place 6-10,000 years ago is the cause of all blue eyes.

Even if you don't have heterochromia (given that it is quite a rare condition), knowing where your blue eyes came from is definitely satisfying.

Ever since testing my DNA with AncestryDNA, I am informed about my health and family history. I anticipate that this priceless information may eventually be part of everyday living.

To get your own Gene Heritage report, visit http://www.geneheritage.com/