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Genetics behind hazel eyes?

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Genetics behind hazel eyes?

Postby Montario » Fri Aug 03, 2012 10:00 pm

Hey everyone,

I am asking this question as I am interested and am wondering if there is a possibility knowing if I carry a recessive gene for eye color. My father, his ethnical background living near the equator has dark brown eyes (his whole side of the family having that too). My mothers side howerver is a very different story. My Great Grandmother and Great Grand Father (grandmas side) both have blue eyes and of course passed it onto my grandmother (bb, bb). My grandfather however has brown eyes so of course he has at least 1 allele for brown eyes, the other unknown. Now, my mother however has hazel eyes (green with small specs of brown at times) which confuses me a lot as to how she got that and what her alleles are (although I am sure she received 1 allele for blue eyes from her mother). I of course have brown eyes because of the dominant genes from my father. So my genetic combination would be B (brown eyes) and ? (Recessive)? There was this theory that appeared multiple times on the internet about the genetics behing hazel eyes, saying that there is a new undiscovered modifier gene 'M' which produced more melanin for the 'G' (green eye gene) producing an eye color that is lighter than brown, but darker than green. There is also an 'm' gene which does no effect. It then states the list of genetic combinations which in theory would result in hazel eyes. They all consisted of RECESSIVE alleles for eye color. The two combinations which my mother could only possibly have were GbMm and Gbmm as bbmm and bbMm resulted in blue eyes, my mother does not have that. From this I would assume that my grandmother would have passed a blue eye gene to my mother and my grandfather a green eye gene, but then with the modifiers making my mothers eyes hazel. I am not sure about this though as many people have stated to get hazel eyes despite both their mother, father and grandparents having brown eyes. From this theory, brown eye genes have no role in creating hazel eyes which makes me even more confused. As for now I believe this theory as it makes sense in most cases but even if the theory IS completely correct (which is quite likely at the moment), could my mother be heterozygous for brown and blue eyes rather than blue and green eyes? If not and she does carry only recessive genes (which according to this theory is true), what would could she have passed on to me? Would she have passed the 'modifiers' too? I know this question was a bit long winded but I would be glad if people could help me out :D. I'm wondering if it is possible for me to have a child with blue or green eyes other than just brown. Thanks!

Here is the link of the theory: ... 16272.aspx
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Postby Darby » Tue Aug 07, 2012 1:48 am

From doing many genetic classes, my take is that there are actual hazel alleles that produce a greenish-brown, but a combination of a light brown and a darker green will get it as well.
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